{"id": "q_CARDIAC1_00", "question": "Which cardiac chambers are typically imaged on the short-axis view?", "golden_answers": [3], "choices": ["RA and RV", "RA and LA", "LA and LV", "RV and LV"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "The short axis view is typically used to show the left and right ventricles."}}
{"id": "q_CARDIAC1_01", "question": "What structure is optimally displayed on the so-called “candy-cane” view?", "golden_answers": [0], "choices": ["Thoracic aorta", "Circumflex artery", "Left main coronary artery", "Right coronary artery"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "The candy-cane view is an oblique sagittal section that lays out the ascending, transverse, and descending thoracic aorta and its proximal branches."}}
{"id": "q_CARDIAC1_02", "question": "Why might one wish to start two IV’s prior to MRI if stress testing is being performed?", "golden_answers": [2], "choices": ["The second serves as backup in case the first IV fails.", "The total amount of fluid and medications required during the exam exceed the capacity of a single average-bore IV.", "Gadolinium contrast and adenosine cannot be given through the same line.", "The second IV is needed for blood sampling during the exam."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "Gadolinium and adenosine cannot be given through the same line, so two separate IVs are required. Separate lines are optional if regadenoson or dobutamine are used."}}
{"id": "q_CARDIAC1_03", "question": "Which of the following foods and medications should be discontinued at least 12-24 hours before a stress MRI?", "golden_answers": [2], "choices": ["Nitroglycerin", "Calcium-channel blockers", "Caffeinated beverages", "Quinidine"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Patients should be advised not to consume stimulants such as coffee, tea, caffeinated sodas, energy drinks, and chocolate within 12-24 hours of the scan.  These can interfere with the efficacy of the pharmacological stress testing and interpretation of the examination."}}
{"id": "q_CARDIAC1_04", "question": "What is the most common EKG change noted when a patient is placed in an MRI?", "golden_answers": [2], "choices": ["Reduction of the R-wave", "Inversion of the R-wave", "Elevation of the T-wave", "ST-segment elevation"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Although all the above phenomena can occur, elevation of the T-wave is most frequently observed. This elevation may be so marked that the T-wave actually becomes larger than the QRS-complex."}}
{"id": "q_CARDIAC1_05", "question": "What is the cause of the EKG changes described above?", "golden_answers": [0], "choices": ["Ionic currents induced by thoracic blood flow", "Susceptibility effects", "Stimulation of accessory cardiac conduction pathways", "Induced currents in the EKG leads"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 4.0, "hint": "This magnetic field effect on the EKG does not originate in the heart itself, but represents a superimposed voltage within blood in the descending thoracic aorta which has been induced by its flow in the magnetic field.  The induction of a voltage in a conductive fluid flowing through a magnetic field is called the magnetohydrodynamic (MHD) effect."}}
{"id": "q_CARDIAC1_06", "question": "Which EKG wave is primarily used for cardiac triggering?", "golden_answers": [2], "choices": ["P-wave", "Q-wave", "R-wave", "T-wave"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 4.0, "hint": "Cardiac gating is typically performed using detection of the R-wave since this is usually the most prominent feature of the EKG. The R-wave coincides with the beginning of ventricular systole."}}
{"id": "q_CARDIAC1_07", "question": "The R-wave corresponds to what cardiac event?", "golden_answers": [1], "choices": ["Beginning of atrial contraction", "Beginning of ventricular systole", "Peak contraction of the ventricle", "Beginning of ventricular diastole"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 4.0, "hint": "The R-wave coincides with the beginning of ventricular systole."}}
{"id": "q_CARDIAC1_08", "question": "If the heart rate is 100 bpm, what is the length of the R-R interval in milliseconds?", "golden_answers": [2], "choices": ["60 ms", "100 ms", "600 ms", "1000 ms"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 4.0, "hint": "Over 1 minute = 60 seconds, there are 100 beats marked by R waves.  The R-R interval is therefore 60s /100 = 0.6 s or 600 ms."}}
{"id": "q_CARDIAC1_09", "question": "In the patient above with a heart rate of 100 bpm, which of the following TR values would not be available for a prospectively gated sequence?", "golden_answers": [1], "choices": ["600 ms", "900 ms", "1200 ms", "1800 ms"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "The repetition time (TR) in a prospectively gated sequence cannot be freely set but must be a multiple of the average R-R interval. Thus for a patient with heart rate = 100, the only choices for TR would be 600 ms, 1200 ms, 1800 ms, etc."}}
{"id": "q_CARDIAC1_10", "question": "Continuing the above example in the patient with HR = 100 bpm, what would be the TR if a gating factor of 4 were chosen?", "golden_answers": [3], "choices": ["125 ms", "600 ms", "1200 ms", "2400 ms"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 4.0, "hint": "The R-R multiple chosen is called the gating factor. So, if the average R-R interval were 600 ms, the corresponding TR value would be 600 x 4 = 2400 ms."}}
{"id": "q_CARDIAC1_11", "question": "In a gated study, the time between the first R-wave and the beginning of data acquisition is known as the", "golden_answers": [2], "choices": ["Trigger window", "Acquisition window", "Trigger delay", "Quiescent interval"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Trigger delay is the time interval between the first R-wave and the beginning of data acquisition."}}
{"id": "q_CARDIAC1_12", "question": "Which of the following is not an advantage of retrospective gating compared to prospective gating?", "golden_answers": [3], "choices": ["TR is not restricted to be a multiple of the R-R interval", "Data acquired during arrythmias can be rejected.", "Data acquired during patient motion can be rejected.", "Magnetohydrodynamic distortions in the EKG can be corrected."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "All are true advantages except (d)."}}
{"id": "q_CARDIAC1_13", "question": "For cardiac imaging navigator pulses are most commonly placed", "golden_answers": [0], "choices": ["On the dome of the right hemidiaphragm", "On the dome of the left hemidiaphragm", "On the left ventricle", "On the chest wall"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "Navigator pulses are typically applied so as to excite 1-dimensional beams or 2-dimensional planes of tissue. Although navigators may be placed over the heart directly, more commonly they are placed to intersect the right hemidiaphragm at its dome."}}
{"id": "q_CARDIAC1_14", "question": "Which one of the following statements about double IR sequences for cardiac imaging is true?", "golden_answers": [1], "choices": ["The first 180°-pulse is spatially selective, while the second 180°-pulse is non-selective.", "Blood suppression requires outside blood flowing in and displacing blood initially within the slice.", "Both blood and fat signals are suppressed.", "Short TI values are required when the heart rate is slow."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "The first inverting pulse is spatially non-selective, while the second pulse is spatially selective, so (a) is false. Inflow of outside blood is a critical requirement for DIR to function properly, so (b) is true. DIR does not suppress fat, so (c) is false. Finally, long (not short) TI values are required when the heart rate is slow."}}
{"id": "q_CARDIAC1_15", "question": "An advantage of triple IR over double IR for cardiac imaging is", "golden_answers": [0], "choices": ["Suppression of pericardial and mediastinal fat", "Shorter imaging times", "More freedom on choice of TI values", "Improved T1 contrast"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Suppression of fat using a third inverting pulse is the primary advantage for triple IR. It comes with limitations, including longer imaging times, less choice on TI values, and replacement of T1 contrast by T2 contrast."}}
{"id": "q_CARDIAC1_16", "question": "How many distinct segments are enumerated in the American Heart Association (AHA) standard model for left ventricular anatomy that are displayed on polar/target/bull’s eye plots?", "golden_answers": [1], "choices": ["15", "17", "19", "21"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 4.0, "hint": "There are 6 basal, 6 middle and 5 apical segments adding to a total of 17."}}
{"id": "q_MRA-I_00", "question": "Which of the following methods is considered a “dark blood” MRA technique?", "golden_answers": [3], "choices": ["Time-of-flight MRA", "Gadolinium-enhanced MRA", "SSFP MRA", "Susceptibility-weighted MRA"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Dark (\"black\") blood MRA techniques suppress signal from flowing blood while maintaining high signal in the surrounding stationary tissues, thus rendering the vessels black. Of those listed, only susceptibility-weighted MRA is a black blood technique."}}
{"id": "q_MRA-I_01", "question": "Which of the following methods is not a “bright blood” MRA technique?", "golden_answers": [1], "choices": ["Phase-contrast MRA", "Double inversion recovery MRA", "Arterial spin-labeled MRA", "Ferumoxytol-enhanced MRA"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Single, double, or even triple 180°-inversion pulses may be used to suppress the signal from blood and other tissues (such as fat or myocardium) based on their respective T1 values. Black blood IR methods are most commonly used for cardiac and vessel wall imaging."}}
{"id": "q_MRA-I_02", "question": "Which of the following is not an advantage of dark-blood compared to bright-blood MRA techniques?", "golden_answers": [2], "choices": ["Less overestimation of stenosis", "Better delineation of vessel walls", "Better sensitivity to low-flow states", "Fewer pulsation artifacts"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Dark-blood MRA has some unique advantages compared to bright-blood techniques. Flow separation and turbulence, which cause unwanted signal losses and overestimation of stenoses on bright-blood MRA, paradoxically improve image quality on dark-blood MRA. Because intraluminal signal is suppressed, vessels containing \"black blood\" do not generate pulsation (ghosting) artifacts. Additionally, the lack of intraluminal signal allows the walls of vessels (or cardiac chambers) to be clearly delineated. For these reasons, dark-blood techniques are predominantly used in cardiac imaging and for evaluation of diseases of the vessel wall (atherosclerotic plaque and dissection). Although an excellent method for imaging high-flow vessels, dark-blood techniques are less sensitive to slower flow states. \"Black\" blood is difficult to separate from adjacent low-signal non-vascular structures, such as calcifications, cortical bone, and air."}}
{"id": "q_MRA-I_03", "question": "What is the purpose of the so-called “traveling sat” pulses in 2D-TOF MRA?", "golden_answers": [0], "choices": ["To reduce venous contamination", "To maximize contrast between stationary tissues and blood", "To minimize signal losses from phase dispersion", "To increase signal from inflowing spins"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "These sat pulses are used to suppress venous signal that would normally flow into each slice."}}
{"id": "q_MRA-I_04", "question": "What is the purpose of using moderate-to-large flip angles (30°−60°) in 2D-TOF-MRA sequences?", "golden_answers": [1], "choices": ["To reduce venous contamination", "To maximize contrast between stationary tissues and blood", "To minimize signal losses from phase dispersion", "To increase signal from inflowing spins"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Larger flip angles produce more magnetic saturation of stationary tissues within the imaged volume, and thus maximize contrast with inflowing blood."}}
{"id": "q_MRA-I_05", "question": "Concerning optimal parameter selection for TOF MRA sequences, which of the following statements is true?", "golden_answers": [2], "choices": ["TR should be very long to insure the greatest degree of inflow enhancement.", "TE should be very long to increase vascular signal from T2 effects.", "Slice orientation should be perpendicular to the direction of flow.", "Flip angle (α) should be very small to increase tissue saturation."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Only (c) is true. The benefits of very long TR to improve inflow enhancement is offset by increased signal from background tissue.  TE should be short to reduce spin-phase losses. Flip angles should be moderate to large to decrease tissue from static tissues."}}
{"id": "q_MRA-I_06", "question": "Blood in an artery with mean velocity of 50 cm/s flows perpendicularly into a 2-cm-thick slice.  At what value of TR is flow-related enhancement maximized?", "golden_answers": [3], "choices": ["10 ms", "20 ms", "30 ms", "40 ms"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 4.0, "hint": "Maximum flow-related enhancement occurs when inflowing blood completely replaces that present in a given slice.  When flow is perpendicular to the slice, maximum enhancement occurs when V  ≥  d / TR, or equivalently, when TR  ≥  d /V.  For d = 2 cm and V = 50 cm/s, this means a TR  ≥ 2/50 s = 0.04 s = 40 ms"}}
{"id": "q_MRA-I_07", "question": "Concerning magnetization-transfer enhanced MRA, which statement is false?", "golden_answers": [0], "choices": ["It is effective for both time-of-flight and phase-contrast MRA", "It is effective for both non-contrast and contrast-enhanced MRA", "Small vessel detail is improved", "Image acquisition time is slightly prolonged."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "MT-MRA is used only for TOF and contrast-enhanced MRA. It offers no benefit for PC-MRA."}}
{"id": "q_MRA-I_08", "question": "Concerning variable (ramped) pulses, which statement is true?", "golden_answers": [2], "choices": ["They are useful in both 2D and 3D TOF MRA.", "Their flip angles are designed to decrease linearly along the direction of flow.", "They are designed to produce greater saturation of stationary tissues deep in the slab.", "They are designed to increase the absolute signal of flowing blood deep in the slab."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Variable (ramped) RF pulses address the progressive loss of MRA signal from vessels extending deep into a 3D-TOF slab. (They are not used for 2D TOF). The flip angle is designed to increase along the direction of flow, producing greater saturation of stationary tissues deep in the slab. (Answer c is correct).  They also suppress blood slightly, but not as much as stationary tissues."}}
{"id": "q_MRA-I_09", "question": "A common artifact seen with MOTSA MRA is called", "golden_answers": [0], "choices": ["The venetian blind artifact", "The stair-step artifact", "The velocity aliasing artifact", "The ringing (Maki) artifact"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "Because each MOTSA slab is acquired at separate times, exact registration of position and signal intensity of adjacent slabs may not be possible. This gives rise to the so-called venetian blind artifacts characteristic of this technique."}}
{"id": "q_MRA-I_10", "question": "A common artifact seen with 2D-TOF MRA is called", "golden_answers": [1], "choices": ["The venetian blind artifact", "The stair-step artifact", "The velocity aliasing artifact", "The ringing (Maki) artifact"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "The stair-step artifact is common on 2D-TOF MRA because patient motion between slices."}}
{"id": "q_MRA-I_11", "question": "In subclavian steal syndrome, the blood flow in one of the two vertebral arteries becomes reversed.  What will be the appearance of this reversed flow vertebral artery on a 2D-TOF MRA of the neck?", "golden_answers": [3], "choices": ["Its appearance will be identical to the contralateral (normally flowing) vertebral artery.", "It will appear paradoxically brighter than contralateral vertebral artery.", "It will appear slightly less bright than the contralateral vertebral artery.", "It will be non-visualized, suggesting an occlusion."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "2D-TOF sequences utilize traveling saturation pulses upstream from the imaged slice to eliminate venous contamination.  In the neck, these pulses effectively eliminate signal in the jugular and other deep veins, but will also eliminate signals from arterial flows whose directions have been reversed. So (d) is the correct answer."}}
{"id": "q_MRA-I_12", "question": "Why might a phase-contrast (PC) MRA of the head be preferred over a TOF MRA in a patient with cerebral hemorrhage?", "golden_answers": [2], "choices": ["The spatial resolution of PC MRA is much higher.", "PC MRA has been shown to be more accurate in the detection of aneurysms.", "T1-shine through of a hematoma does not affect PC MRA but may obscure TOF MRA.", "The acquisition time of PC MRA is much shorter than equivalent TOF techniques."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "TOF MR angiographic images are displayed using a maximum intensity projection (MIP) algorithm. In addition to bright blood vessels, any other material with high signal intensity will \"shine through\" and \"contaminate\" the MIP image. Since underlying TOF MRA pulse sequences are T1-weighted, short T1 materials (hematoma, gadolinium, and fat) are primarily responsible for this phenomenon.  PC MRA, however, relies on phase shift differences due to motion, and does not suffer from shine-though."}}
{"id": "q_MRA-I_13", "question": "The underlying mechanism of phase-contrast MRA is based on", "golden_answers": [0], "choices": ["Bipolar flow-encoding gradients", "Unipolar flow-encoding gradients", "RF-phase cycling between excitations", "Use of a linear gradient with constant slope along the phase-encoding axis"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "PC MRA utilizes bipolar gradients, applied along one or more directions along which flow information is desired.  A stationary spin subjected to such a gradient pair will experience no net phase shift, but a moving spin will have a net phase shift proportional to its velocity."}}
{"id": "q_MRA-I_14", "question": "The units of the VENC (velocity-encoding) parameter for PC MRA are", "golden_answers": [1], "choices": ["dimensionless", "cm/s", "cm²/s", "cm/s²"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "VENC is a velocity, so the correct answer is (b), cm/s."}}
{"id": "q_MRA-I_15", "question": "If the VENC in a PC MRA is set at 60 cm/s, the strength and duration of the bipolar gradients are adjusted so that blood flowing at 60 cm/s has a phase shift of", "golden_answers": [2], "choices": ["+60º", "+90º", "+180º", "+360º"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "For a given VENC, the bipolar gradients are adjusted so blood velocities at this level are assigned a +180º phase shift."}}
{"id": "q_MRA-I_16", "question": "If the VENC is set to 50 cm/s, and the actual forward flow blood velocity is 75 cm/s, what velocity will be displayed on the PC MRA?", "golden_answers": [3], "choices": ["+50 cm/s", "+75 cm/s", "+25 cm/s", "−25 cm/s"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 4.0, "hint": "If the chosen value of VENC is 50 cm/sec, the bipolar gradient is adjusted so that flows of +25 and +50 cm/sec are assigned a phases of +90° and +180° respectively. If the actual velocity is +75 cm/sec, this flow will be mapped to +270°, a value that cannot be distinguished from a phase shift of −90°. Instead of representing the +75-cm/sec flow as its actual velocity, the computer will assign it a flow of 25 cm/sec in the opposite direction!"}}
{"id": "q_MRA-I_17", "question": "A PC MRA using bipolar gradients whose VENCs are properly set determines that velocities in the three cardinal directions are vx = −52 cm/s,  vy = +24 cm/s, and vz = +72 cm/s.  When displayed as a magnitude (speed) image, the brightness of each voxel is proportional to", "golden_answers": [1], "choices": ["148 cm/s", "92 cm/s", "72 cm/s", "44 cm/s"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 4.0, "hint": "By definition, speed = √{v²x + v²y + v²z} = √{(−52)² + (+24)² + (+72)²} = √{8464} = 92 cm/s."}}
{"id": "q_MRA-I_18", "question": "Concerning the accuracy of PC-MRA velocity measurements compared to Doppler in medium to large vessels, the two measurements generally lie within what percentage of each other?", "golden_answers": [1], "choices": ["Less than 1%", "About 5%", "15% - 25%", "More than 25%"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "The two measurements are generally within about 5% of each other."}}
{"id": "q_MRA-I_19", "question": "Which of the following situations would velocity measurements by PC MRA be the most accurate?", "golden_answers": [0], "choices": ["Imaging plane perpendicular to the direction of flow", "Pixel size close to the vessel diameter", "Turbulent flow", "Sampling of great vessel flows using 8 frames per cardiac cycle."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "Measurement of flow velocities is most accurate when the vessel is perpendicular to the plane of imaging. When the pixel size exceeds one-third of the vessel diameter, significant partial volume effects may occur with underestimation of flow and peak velocities.  When velocities change suddenly in magnitude, direction, or both, as they do in turbulence, accuracy of flow measurements declines. If the data sampling rate throughout the cardiac cycle is too low, flow may not be measured at its peak value. For imaging the great vessels at least 16 frames per cardiac cycle should be sampled"}}
{"id": "q_MRAIIQUIZ_00", "question": "Which statement about Gated 3D-FSE MRA techniques is incorrect?", "golden_answers": [2], "choices": ["They can be gated either to the EKG or peripheral pulse.", "Co-registered images are obtained in diastole and systole.", "Diastolic and systolic images are added together to produce the angiogram.", "Image contrast is based on the long T2 of blood."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "The sequence is cardiac gated either to the EKG or peripheral pulse. Co-registered images are obtained in diastole and systole.  During diastole, the signal in both arteries and veins is high reflecting the long T2 of blood. During systole, venous signal remains high but arterial signal drops due to flow-related signal loss. Subtraction (not addition) of the systolic from the diastolic images results in a pure arterial image."}}
{"id": "q_MRAIIQUIZ_01", "question": "Which of the following is not a disadvantage of 3D-FSE MRA?", "golden_answers": [0], "choices": ["Required use of gadolinium contrast.", "Overestimation of stenoses", "Vascular pulsation artifacts", "Sensitivity to cardiac arrythmias"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Option (a) is false. The main advantage of 3D-FSE MRA is that it does not require contrast, a property that may be important in patients with renal insufficiency (where receiving gadolinium might place them at risk for nerphogenic systemic fibrosis)."}}
{"id": "q_MRAIIQUIZ_02", "question": "Intravascular contrast in balanced steady-state free precssion (b-SSFP) MRA is primarily related to which property of blood?", "golden_answers": [3], "choices": ["High spin-density", "Long T1", "Long T2", "High T2/T1 ratio"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "b-SSFP MRA exploits the differences between the relatively high T2/T1 ratio of blood compared to most other tissues."}}
{"id": "q_MRAIIQUIZ_03", "question": "What is the main reason b-SSFP MRA sequences are not routinely used in intracranial imaging?", "golden_answers": [1], "choices": ["Its spatial resolution is insufficient to resolve the major intracranial vessels.", "The signal from intracranial vessels is obscured by high signal from nearby CSF.", "Intracranial vessels typically demonstrate turbulent flow which disrupts the SSFP.", "Susceptibility artifacts from the skull base produce troublesome zebra-stripe artifacts over most of the brain."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Like blood, CSF has a high T2/T1 ratio and so will appear bright on SSFP MRA sequences.  Since the arteries at the base of the brain are literally “bathed” in CSF, this is the main reason the sequences are not commonly used intracranially."}}
{"id": "q_MRAIIQUIZ_04", "question": "The purposes of the inversion pulse(s) used in inflow-enhanced, IR-prepped 3D-SSFP MRA include all of the following except", "golden_answers": [3], "choices": ["Nulling of signal from water-containing background tissue.", "Nulling of signal from fat", "Nulling of signal from venous blood", "Hyperpolarization of incoming arterial spins."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "The inversion pulses allow arterial inflow to be relatively accentuated due to background and venous suppression, not because of hyperpolarization."}}
{"id": "q_MRAIIQUIZ_06", "question": "Which of the following statements about the Quiescent-Interval Single-Shot (QISS) MRA is incorrect?", "golden_answers": [0], "choices": ["It does not require cardiac gating.", "It does not utilize gadolinium contrast.", "It is primarily used for extremity MRA", "Unsaturated blood enters the imaged slice during the quiescent interval (QI)"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "QISS is a cardiac-gated, non-contrast inflow technique bearing some similarities to 2D time-of-flight (TOF) and inflow-enhanced SSFP MRA. It is especially designed for peripheral MRA. Fresh (fully magnetized/unsaturated) enters the slice during the quiescent interval, with arterial signal generated by a balanced-SSFP sequence."}}
{"id": "q_MRAIIQUIZ_07", "question": "Which of the following statements about contrast-enhanced (CE)-MRA is false?", "golden_answers": [2], "choices": ["If scanning is performed too early after injection, inadequate vascular visualization may result.", "Scanning performed too late after injection may result in venous contamination.", "If you incorrectly time the bolus on the first acquisition, you can wait 10 minutes and repeat the injection.", "Signal generation is typically performed using a 3D T1-weighted spoiled gradient echo sequence with short TR and TE."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "Ideally, CE-MRA should be performed when the contrast agent arrives in the vessel at or near its peak concentration. To early and you don’t see the vessel; too late and you may get venous contamination.  You only get one chance to get it right and cannot repeat the sequence until the next day or two when the gadolinium clears out of the system."}}
{"id": "q_MRAIIQUIZ_08", "question": "What is fluoroscopic triggering for MRA?", "golden_answers": [3], "choices": ["A method that uses information from an x-ray fluoroscope to assist in timing of the gadolinium bolus.", "A method to estimate timing of arrival of a small (1-2 ml) test bolus of gadolinium.", "A 3D-phase contrast method to estimate the distribution of contrast throughout the entire imaging volume.", "A method providing a “fluoroscopic-like” MR image during transit of a full contrast bolus at which time the MRA acquisition can begin."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "In fluoroscopic triggering the full bolus of contrast (~20 mL) is administered while a fluoroscopic-like picture of the artery of interest is acquired using a rapid 2D gradient-echo technique. The technologist can then initiate MRA acquisition or the triggering can be done automatically."}}
{"id": "q_MRAIIQUIZ_09", "question": "The preferred k-space sampling method used for most 3D-CE-MRA sequences is called", "golden_answers": [0], "choices": ["Elliptical-centric ordering", "Linear ordering", "Sequential ordering", "Stochastic ordering"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Elliptical-centric ordering is now the preferred k-space sampling method used for most CE-MRA examinations. Linear methods may still be used on older equipment and for MRA of the distal extremities where arrival of the contrast bolus may be prolonged or its exact timing difficult to predict."}}
{"id": "q_MRAIIQUIZ_10", "question": "What type of k-space sampling is used in modern time-resolved MRA sequences like TRICKS and TWIST?", "golden_answers": [2], "choices": ["Zig-zag", "Cartesian", "Radial", "Spiral"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Modern time-resolved MRA techniques typically use radial sampling schemes, acquiring 3D k-space in segmented round or oval \"cylinders\"."}}
{"id": "q_MRAIIQUIZ_11", "question": "Which technical component is not a feature used in modern time-resolved MRA sequences like TRICKS and TWIST?", "golden_answers": [0], "choices": ["3D-SSFP acquisition", "Both phase- and read-conjugate symmetry", "Elliptical-centric ordering", "Parallel imaging"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Option (a) is incorrect. Time-resolved MRA methods have at their core a 3D-spoiled GRE sequence with thin slices, very short TRs and TEs, low flip angles, use of both read- and phase-conjugate symmetry, parallel imaging acquisition, and zero-interpolation filling in the slice direction."}}
{"id": "q_MRAIIQUIZ_12", "question": "What causes the subclavian artery “pseudo-stenosis” artifact on CE-MRA?", "golden_answers": [1], "choices": ["Compression of the subclavian artery by the subclavian vein", "Susceptibility effects due to residual gadolinium in the subclavian vein", "Turbulence at its junction with the axillary artery", "Reflux due to retrograde flow from the vertebral artery into the subclavian artery"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "A focal irregularity in the subclavian artery mimicking stenosis may occur ipsilateral to the side of contrast injection. This is a susceptibility (T2*) effect due to residual gadolinium in the adjacent subclavian vein, more commonly seen on the left side than right."}}
{"id": "q_MRAIIQUIZ_13", "question": "What is the cause of the ringing (Maki) artifact on CE-MRA?", "golden_answers": [1], "choices": ["Gibbs (truncation) phenomenon", "Central region of k-space scanned before arrival of the contrast bolus", "Central region of k-space scanned too long after arrival of contrast bolus", "Vascular pulsation"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "If the central region of k-space is scanned before arrival of the contrast bolus, the vessel will appear dark in the middle, with only its edges demonstrating enhancement.  Scanning too early produces this artifact originally described by Maki et al."}}
{"id": "q_MRFLOW_00", "question": "Bulk blood flow (Q) through a certain point in the vascular tree within a given period of time is measured in what units?", "golden_answers": [3], "choices": ["cm/s", "cm/s²", "cm²/s", "cm³/s"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "Bulk flow is a volume per unit time and is expressed in units of cm³/s."}}
{"id": "q_MRFLOW_01", "question": "What is the approximate bulk blood flow (Q) passing through a 2 cm diameter artery where the average velocity is 50 cm/s?", "golden_answers": [3], "choices": ["25 cm³/s", "50 cm³/s", "100 cm³/s", "160 cm³/s"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "The cross-sectional area (A) of the vessel is πr² = π (1 cm)² = 3.14 cm². So the bulk blood flow (Q) = V x A = 50 cm/sec x 3.14 cm² = 157 cm³/s."}}
{"id": "q_MRFLOW_02", "question": "In what part of a vessel is the blood flow the slowest?", "golden_answers": [0], "choices": ["Adjacent to the wall of the vessel", "In the center of the vessel", "Half-way between the wall and center", "The blood flow is the same across the entire vessel."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "Near the vessel wall where fluidic shearing and frictional forces are greatest, the blood flow will be nearly zero. Centrally within the lumen, blood flow will be most rapid."}}
{"id": "q_MRFLOW_03", "question": "Which blood vessel normally demonstrates a prominent reversal of flow during the cardiac cycle?", "golden_answers": [1], "choices": ["Vertebral artery", "Ascending thoracic aorta", "Middle cerebral artery", "Renal artery"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "The thoracic aorta has prominent reversal of flow during diastole as the coronary circulation is filled. The brain and kidneys have low vascular resistance; thus, carotid and renal arterial vessels demonstrate high forward flows even during diastole."}}
{"id": "q_MRFLOW_04", "question": "Which blood vessel has the greatest peak velocity?", "golden_answers": [0], "choices": ["Thoracic aorta", "Abdominal aorta", "Carotid artery", "Renal artery"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 1.0, "hint": "The ascending aorta has the highest average peak velocities of the major vessels; typical values are 150-175 cm/sec. Flow in the distal aorta and iliac vessels slows to the 100-150 range, whereas peak velocities in the proximal carotid, brachial, and superficial femoral arteries are about 80-110 cm/sec."}}
{"id": "q_MRFLOW_05", "question": "What happens to peak velocities as a vessel goes becomes increasingly stenotic?", "golden_answers": [3], "choices": ["They decrease.", "They increase.", "They remain the same.", "They increase initially then decrease."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "As vessels become increasingly stenotic their peak velocities initially increase (due to the Bernoulli effect). In extremely high-grade stenosis, however, vascular resistance becomes so high that the flow rates and velocities fall just before total occlusion is reached."}}
{"id": "q_MRFLOW_06", "question": "In ideal laminar flow the distribution of velocities in cross-section across a vessel should be", "golden_answers": [2], "choices": ["Linear", "Constant", "Parabolic", "Hyperbolic"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "Laminar flow refers to a predictable distribution of flow velocities in layers (lamina) that parallel the vessel wall.  Theoretically, the distribution of velocities in a perfectly straight, nonbranching vessel with nonpulsatile flow should be parabolic in cross-section."}}
{"id": "q_MRFLOW_07", "question": "In which anatomic situation would you not expect to find vortex flow?", "golden_answers": [2], "choices": ["Distal to a carotid artery stenosis", "In the proximal (ascending) aorta", "In the distal thoracic aorta", "In an abdominal aortic aneurysm"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "Vortex flow refers to localized swirling or stagnant blood flow that has separated from the central streamlines within a vessel. Such vortices, also called flow eddies, frequently occur at vascular bifurcations and distal to areas of stenosis. Vortex flow is prominent in the ascending aorta, as jets of blood are expelled and swirl around during each cardiac contraction. They are less likely in the distal thoracic aorta, so the correct answer is (c)."}}
{"id": "q_MRFLOW_08", "question": "Which statement about the Reynolds number (Re) in ideal fluids is true?", "golden_answers": [3], "choices": ["Values of Re < 2000 predict turbulent flow.", "Values of Re > 2500 predict laminar flow.", "Re is a velocity with units of cm/sec.", "Re is a dimensionless parameter."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "The Reynolds number (Re) is a dimensionless parameter used to predict flow characteristics in ideal fluids. (Answer d is correct). Values of Re less than 2000 predict that flow will be laminar, whereas values greater than 2500 usually indicate that flow will be turbulent."}}
{"id": "q_MRFLOW_09", "question": "In which situation would you be more likely to see turbulent flow?", "golden_answers": [1], "choices": ["In a vessel with a small diameter", "In a vessel with rapid blood velocities", "In a vessel with elevated blood viscosity", "In the stump of a newly occluded vessel"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "The probability of turbulent flow is proportional to the Reynolds number (Re), being directly proportional to blood velocity and vessel diameter, and inversely proportional to blood viscosity. So choice (b) is correct."}}
{"id": "q_MRFLOW_10", "question": "Which one of the following flow-related phenomena is considered a time-of-flight (TOF) effect?", "golden_answers": [0], "choices": ["High intravascular signal in an entry slice.", "Signal loss due to in-plane flow within an imaging gradient.", "Signal loss due to turbulent flow in an aneurysm.", "High signal in a vessel due to gradient moment nulling."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "Time-of-flight (TOF) effects refer to signal variations resulting from the motion of protons flowing into or out of an imaging volume during a given pulse sequence. High intravascular signal in an entry slice (choice a) is a type of TOF known as flow-related enhancement. The other choices are all spin-phase effects."}}
{"id": "q_MRFLOW_12", "question": "Which statement concerning high-velocity signal loss (“washout”) is incorrect?", "golden_answers": [2], "choices": ["High-velocity signal loss is considered a time-of-flight effect.", "It is typically seen in arteries and larger veins flowing perpendicular to the plane of imaging.", "It is seen primarily in gradient echo imaging sequences.", "It can occur anywhere in the imaging slab and is not confined to the end slices."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "Answer (c) is incorrect. High-velocity signal loss is typically seen on spin-echo sequences where flowing blood must receive both 90° and 180° pulses to generate a signal.  Gradient echo sequences use single RF-pulses with gradient refocusing."}}
{"id": "q_MRFLOW_13", "question": "The total phase gained by a proton moving for time (t) at constant velocity (v) through a constant gradient of strength (G) is proportional to", "golden_answers": [1], "choices": ["t", "t²", "v²", "G²"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "The phase shift experienced by a moving spin will be proportional to its velocity, the strength of the applied gradient, and the square of the length of time it moves within that gradient."}}
{"id": "q_MRFLOW_14", "question": "A radiologist interpreting a head MRI in a patient with suspected stroke dictates: “A flow-void is noted in the basilar artery.” What does this mean?", "golden_answers": [2], "choices": ["No blood flow is present in the basilar artery.", "Some flow in the basilar artery may be present, but it is very weak.", "The basilar artery contains flowing blood.", "A thrombus is present in the basilar artery."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "“Flow void” is a widely used term referring to low signal in vessels that contain vigorously flowing blood, and is due to a combination of time-of-flight and spin-phase effects. Although most specialists are familiar with this term, it has the potential for confusion among less sophisticated members of the health care team, who may falsely interpret it to mean absence of flow."}}
{"id": "q_MRFLOW_15", "question": "Which of the following statements is not a reason gradient echo sequences can be used to preserve or accentuate signal from flowing blood?", "golden_answers": [0], "choices": ["Gradient refocusing of spins is slice-selective.", "Relatively short echo times possible with GRE minimize T2* dephasing.", "Sequential mode acquisition with GRE  makes every slice an “entry slice” with flow-related enhancement.", "Moderate-to-large flip angles with GRE saturate stationary tissue and accentuate T2/T1 contrast of blood."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "All are true except (a). In routine SE imaging, at least part of the reason for flow-related signal loss is that spins move out of the section between the 90°- and 180°-(refocusing)-pulses.  In GRE imaging the refocusing is done by means of a gradient reversal that is not slice-selective.  This nonselective refocusing does not result in hyperintensity of incoming spins, however; it merely prevents them from experiencing TOF signal losses."}}
{"id": "q_MRFLOW_16", "question": "Which of the following is not a limitation of the flow compensation (gradient-moment nulling) technique?", "golden_answers": [1], "choices": ["Increased minimum TE", "Increased energy deposition (SAR)", "Inability to correct for nonconstant velocities or acceleration", "Increased stress on gradients"], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 2.0, "hint": "All are true except (b). No extra RF pulses are used, just additional gradient lobes, so no additional energy is deposited by GMN."}}
{"id": "q_MRFLOW_17", "question": "In which situation would refocused misregistered flow signal most likely to be observed?", "golden_answers": [3], "choices": ["In a vessel running parallel to the phase-encode axis.", "In a vessel running perpendicular to the phase-encode axis.", "In sequences with very short TE values.", "In sequences where flow compensation (gradient-moment nulling) is used."], "metadata": {"subject": "Cardiovascular and MRA Quiz", "level": 3.0, "hint": "Flow misregistration is most commonly seen for in-plane vessels running obliquely to the frequency and phase-encoding axes with long TE’s and the use of gradient-moment nulling."}}
{"id": "q_KQUIZ_00", "question": "A point in k-space corresponds to", "golden_answers": [0], "choices": ["The amount of a particular spatial frequency in the entire imaged object", "The amount of a particular spatial frequency at a particular point in the imaged object", "The magnitude and phase of the signal arising from a particular point in the imaged object", "The spin density of the signal arising from the entire imaged object."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "K-space is an array of numbers representing spatial frequencies in the MR image. The individual points (kx,ky) in k-space do not correspond one-to-one with individual pixels (x,y) in the image. Each k-space point contains spatial frequency and phase information about every pixel in the final image."}}
{"id": "q_KQUIZ_01", "question": "Which of the following statements about k-space is false?", "golden_answers": [3], "choices": ["The kx and ky axes of k-space generally correspond to the horizontal (x-) and vertical (y-) axes of the image.", "Each point in k-space contains spatial frequency and phase information about every pixel in the final image.", "Each pixel in the image maps to every point in k-space.", "Points near the center of k-space correspond to points in the center of the image."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "Each point in k-space contains spatial frequency and phase information about every pixel in the final image. So choice (d) is false."}}
{"id": "q_KQUIZ_02", "question": "Which of the following statements about k-space is true?", "golden_answers": [2], "choices": ["The center of k-space provides information about the edges and details of the imaged object.", "The periphery of k-space provides information about the general shape and contour of the object.", "The raw data at the exact center of k-space always has a larger magnitude than any other point.", "k-space must be filled with data in a specific order."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "Only (c) is true. There are two reasons the central area of k-space has the largest magnitude. First, the central row (ky = 0) is acquired with no phase-encoding gradient (and hence no destructive wave interference caused by phase-encoding steps). Secondly, the central column of k-space (kx  = 0) coincides with the peak of the MR echo."}}
{"id": "q_KQUIZ_03", "question": "In routine anatomic MR images, what points in k-space have the lowest amplitudes?", "golden_answers": [0], "choices": ["The four corners", "The center", "The middle of the top and bottom edges", "The middle of the left and right edges"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "Signals from the four corners have the highest spatial frequencies in both directions and correspond to data locations where the MR signals are weakest. For time-savings in spiral imaging, the four corners are often excluded from data sampling with only minimal loss of resolution noted."}}
{"id": "q_KQUIZ_04", "question": "The “k” of k-space refers to “wavenumber”, an index for spatial frequency, which is the number of waves or cycles per unit distance. An acceptable unit for “k” could therefore be", "golden_answers": [1], "choices": ["Cycles per second", "mm−1", "cm/sec", "Line pairs"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "The wavenumber (k) is simply the reciprocal of the wavelength. Since the wavelength is measured in units of distance, the units for wavenumber are (1/distance), such as 1/mm = mm−1. Other acceptable units would include line pairs per mm and cycles per mm."}}
{"id": "q_KQUIZ_05", "question": "Which statement about the location of spatial frequencies in k-space is true?", "golden_answers": [2], "choices": ["A point along the kx axis corresponds to horizontal stripes in the image", "A point along the ky axis corresponds to vertical stripes in the image", "A point at a 45º angle from the the kx axis corresponds to stripes at 45º in the image", "If the imaged object is small relative to the field-of-view, its k-space frequency representation will be mostly confined to the center."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Option (c) is true. Options (a) and (b) are reversed. Concerning incorrect choice (d), the physical size of the object imaged and its frequency expanse in k-space are inversely related. In other words, small objects have ripples far out into the periphery of k-space, while larger objects have their spectral energies more concentrated at the center."}}
{"id": "q_KQUIZ_06", "question": "Consider a conventional 2DFT spin-echo pulse sequence with frequency encoding along the x-axis and phase-encoding along the y-axis. Which statement is false?", "golden_answers": [2], "choices": ["For a given phase-encode step (ky), digitized data from the early part of the echo is placed at the far left side of k-space (negative kx values).", "For a given phase-encode step (ky), digitized data from the early part of the echo is placed at the far right side of k-space (positive kx values).", "For a given phase-encode step (ky), digitized data from the peak of the echo is placed at the the point (kx=0, ky=0).", "For a given phase-encode step (ky), digitized data from the peak of the echo is placed at the the point (kx=0, ky)."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "Option (c) is false, while option (d) is true."}}
{"id": "q_KQUIZ_07", "question": "Concerning the filling of k-space by a conventional 2DFT spin-echo pulse sequence with frequency encoding along the x-axis and phase-encoding along the y-axis, which statement is false?", "golden_answers": [1], "choices": ["The central point of k-space (kx=0, ky=0) corresponds to the constant term in the Fourier representation of the image.", "Except for the central row (ky=0), each row of k-space is acquired with the same constant value of the phase-encoding gradient.", "The central row (ky=0) of k-space is acquired with no phase-encoding gradient.", "The central column of k-space (kx=0) coincides with the peak of the MR echo for each phase-encoding step."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Option (b) is false. In 2DFT spin-echo imaging, the phase encoding gradient is stepped in magnitude from cycle to cycle, not held constant. The other statements are correct."}}
{"id": "q_KQUIZ_08", "question": "The row-by-row filling of k-space by a conventional 2DFT spin-echo pulse sequence is often referred to as what trajectory?", "golden_answers": [0], "choices": ["Cartesian", "Radial", "Zig-Zag", "Blipped"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "Traditionally the Cartesian (row-by-row) method was used nearly exclusively for all pulse sequences, but today many different patterns are widely encountered."}}
{"id": "q_KQUIZ_10", "question": "The non-uniform raw data from a radial or spiral acquisition must be placed into a rectangular (Cartesian) matrix format for efficient computations. This process is referred to as", "golden_answers": [1], "choices": ["Morphing", "Gridding", "Pigeon-holing", "Compressing"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "“Gridding“ is the commonly used term for this process. Although various methods exist, the typical gridding algorithm first involves multiplication of original data with a set of density compensation weights and convolution with a gridding kernel. The resultant data is then interpolated and placed into the uniformly spaced matrix (the \"grid\") where a discrete Fourier transform is performed. Finally, the field-of-view is trimmed and the transformed data multiplied by an apodization correction function."}}
{"id": "q_KQUIZ_11", "question": "How many phase cycles are needed to uniquely differentiate each pixel along a certain direction in an image?", "golden_answers": [1], "choices": ["0,5", "1", "1", "2"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "One full phase cycle is needed to uniquely differentiate each pixel. If there are N pixels of width (Δw) spanning the field-of-view (FOV), then N phase cycles are needed."}}
{"id": "q_KQUIZ_12", "question": "If the data sampling rate is halved in the frequency-encode direction (x), what happens to the spacing (Δkx) between points in k-space?", "golden_answers": [2], "choices": ["It remains unchanged.", "It is halved.", "It is doubled.", "It is quadrupled."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "This is equivalent to sampling every other kx value, so compared to the original pattern, the spacing Δkx) will double  Link to Q&A discussion"}}
{"id": "q_KQUIZ_13", "question": "If the data sampling rate is halved in the frequency encode direction (x), what happens to the field of view in that direction?", "golden_answers": [1], "choices": ["It remains unchanged.", "It is halved.", "It is doubled.", "It is quadrupled."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "We use the formula Δk = 1/FOV. So doubling Δk means the FOV is halved."}}
{"id": "q_KQUIZ_14", "question": "If the data sampling rate is halved in the frequency encode direction (x), what happens to the pixel size in that direction?", "golden_answers": [0], "choices": ["It remains unchanged.", "It is halved.", "It is doubled.", "It is quadrupled."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "The pixel width Δw = 1/ kFOV. As long as the kFOV = 2kmax is unchanged, the pixel width will remain unchanged also."}}
{"id": "q_KQUIZ_15", "question": "Supposed the data sampling rate in the frequency encode direction (x) is unchanged, but the sampling time is reduced so that only the central ⅓ of k-space is sampled. What happens to the pixel width and FOV in that direction?", "golden_answers": [0], "choices": ["The pixel size is tripled and the FOV is unchanged.", "The pixel size is unchanged and the FOV is tripled.", "Both the pixel size and FOV are reduced by ⅓.", "Both the pixel size and FOV are tripled."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Because the data sampling rate is unchanged, Δkx is unchanged and the points are spaced out as before. So since Δk = 1/FOV, the FOVx is unchanged. By sampling only the center ⅓ of k-space, the kFOV is now only ⅓ as large. And since pixel width Δw = 1/ kFOV, this means the pixel width has tripled. Hence answer (a) is correct."}}
{"id": "q_KQUIZ_16", "question": "Suppose that the frequency encoding portion of the 2D spin warp imaging was left alone, but the number of phase-encoding steps was cut in half (while leaving the maximum and minimum amplitudes of the phase-encoding gradient unchanged). What happens to the spacing (Δky) between points in the phase-encode direction (y)?", "golden_answers": [2], "choices": ["It remains unchanged.", "It is halved.", "It is doubled.", "It is quadrupled."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "Cutting the number of phase encode steps (Ny) in half in this scenario doubles the increment between successive steps, so Δky is doubled."}}
{"id": "q_KQUIZ_17", "question": "In the question above, what does the phrase “while leaving the maximum and minimum amplitudes of the phase-encoding gradient unchanged” mean in terms of kFOV in the y-direction?", "golden_answers": [0], "choices": ["It remains unchanged.", "It is halved.", "It is doubled.", "It is quadrupled."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "The phrase basically stipulates that kFOV is unchanged."}}
{"id": "q_KQUIZ_18", "question": "Continuing on with the same scenario as in questions 17 and 18, what happens to the pixel width and the phase FOV?", "golden_answers": [3], "choices": ["The pixel size is doubled and the FOV is unchanged.", "The pixel size is unchanged and the FOV is doubled.", "Both the pixel size and FOV are halved.", "The pixel size is unchanged and the FOV is halved."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "The scenario in these last three questions is to create a rectangular field of view with a 1:2 frequency:phase ratio.  Because Δky is doubled, the FOVy is halved. Furthermore, because both the FOVy and Ny have been reduced by one-half, pixel size in the phase-encode direction (FOVy/ Ny) and overall spatial resolution of the image are also unchanged."}}
{"id": "q_KQUIZ_19", "question": "Concerning obtaining a rectangular field of view by reducing the number of phase encoding steps as described above, which of the following statements is false?", "golden_answers": [2], "choices": ["This option is most beneficial when imaging the spine and extremities.", "Spatial resolution is unchanged.", "Signal to noise ratio is unchanged.", "Wrap-around artifacts in the phase-encode direction are more likely to occur."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "Option (c) is false. Because fewer phase-encoding steps and hence fewer echo signals are acquired, the signal-to-noise ratio (SNR) is proportionately lower compared to full FOV imaging."}}
{"id": "q_KQUIZ_20", "question": "Provided no phase errors occur during data collection, what type of symmetry does k-space exhibit?", "golden_answers": [3], "choices": ["x-axis symmetry", "y-axis symmetry", "z-axis symmetry", "conjugate symmetry"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "Provided no phase errors occur during data collection, k-space possesses a peculiar mirrored property known as conjugate (or Hermitian) symmetry."}}
{"id": "q_KQUIZ_21", "question": "Which statement concerning phase-conjugate symmetry (partial Fourier) imaging is false?", "golden_answers": [0], "choices": ["Over 50% savings in imaging time can be achieved by the use of this technique.", "More than half of the phase-encoding lines must be sampled to correct for phase errors.", "Spatial resolution is preserved.", "For half-Fourier imaging, signal-to-noise is reduced by about 30%."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Phase-conjugate symmetry techniques use data from the top half of k-space to estimate data in the lower half of k-space. In theory, phase-conjugate symmetry allows one to acquire data using only half the normal number of phase-encoding steps, thus potentially reducing imaging time by up to one-half. However, to correct for phase errors, more than half of the phase-encoding lines must be sampled, so the actual time savings is less than 50%."}}
{"id": "q_KQUIZ_22", "question": "Which statement concerning read-conjugate symmetry imaging is false?", "golden_answers": [2], "choices": ["There is no direct time savings.", "Flow and motion artifacts along the frequency-encode direction are reduced.", "Only the first part of the echo is sampled.", "The technique allows for shorter TE values."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "The direction of read-conjugate symmetry is along the readout (frequency-encode) axis. Only the last part of the echo is sampled, so choice (c) is false. The other statements are true."}}
{"id": "q_KQUIZ_23", "question": "Which of the following statements about zero filling is false?", "golden_answers": [1], "choices": ["It may be used either for 2D or 3D imaging", "It is used to expand the imaging matrix in the frequency-encoded direction", "It improves the apparent spatial resolution of the image.", "After the first doubling of matrix size with zeros, no added benefit is realized."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Zero-filling is routinely used to expand the image matrix size in the phase-encoded direction, which may be either within-plane (2D) or through-plane/slab select (3D). Zero filling acts as method to interpolate the signals from neighboring voxels, giving the image a smoother and less \"pixel-ly\" appearance."}}
{"id": "q_PIQUIZ_00", "question": "Which of the following statements about parallel imaging is false?", "golden_answers": [2], "choices": ["It can be used with virtually all pulse sequences.", "It requires multiple receiver coils.", "It can be performed in any direction.", "Its primary purpose is to reduce the number of required phase-encoding steps."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "The allowed direction(s) in which PI can be performed depends on the arrangement of coils in the array. Specifically, the coils must should have different sensitivity profiles along the direction chosen for PI. PI cannot not be used with just a single surface, head, knee, or large body coil having only one pair of quadrature output channels."}}
{"id": "q_PIQUIZ_01", "question": "Which of the following is not a disadvantage of parallel imaging?", "golden_answers": [0], "choices": ["Increased susceptibility artifacts.", "Increased aliasing artifacts.", "Coil calibration artifacts.", "Increased noise in a non-uniform fashion with reduced SNR."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Phase-related distortions in the MR signal due to susceptibility are reduced (not increased) by the PI acquisition and reconstruction process. This is especially advantageous in echo-planar sequences."}}
{"id": "q_PIQUIZ_02", "question": "Comparing image domain PI techniques (like SENSE/ASSET) and k-space PI techniques like (GRAPPA/ARC), which statement is false?", "golden_answers": [1], "choices": ["For high R(acceleration)-values, image domain PI techniques provide slightly higher SNR.", "Image domain PI performs better in heterogeneous body regions (like the chest)", "K-space PI techniques display less aliasing and are more useful when small FOVs are needed.", "K-space PI techniques are more effective at minimizing susceptibility distortions."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Image domain PI techniques like SENSE/ASSET perform poorly in heterogenous body regions. This is because accurate coil sensitivity maps may difficult to obtain.  The lungs are a prime example."}}
{"id": "q_PIQUIZ_03", "question": "What is the proper order of steps in acquiring an image-domain PI image (like SENSE/ASSET)? Abbreviations: A = Acquire partial k-space data; G = Generate coil sensitivity maps; R = Reconstruct individual coil images; U = Unfold/combine partial FOV images.", "golden_answers": [2], "choices": ["A — G — R — U", "G — A — U — R", "G — A — R — U", "A — G — U — R"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "The proper order is Generate/Acquire/Reconstruct/Unfold (c)."}}
{"id": "q_PIQUIZ_04", "question": "What is the proper order of steps in acquiring an k-space PI image (like GRAPPA/ARC)? Abbreviations: A = Acquire partial k-space data; C = Combine data into magnitude image; E = Estimate missing k-space lines; G = generate individual coil images", "golden_answers": [1], "choices": ["A — C — E — G", "A — E — G — C", "E — A — G — C", "E — A — C — G"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "The proper order is Acquire/Estimate/Generate/Combine (b)."}}
{"id": "q_PIQUIZ_05", "question": "Which of the following statements about CAIPIRINHA sequence is false?", "golden_answers": [0], "choices": ["It can be classified as an image-domain PI technique.", "Acceleration factors (R) of 4 are typical.", "It is most commonly used for 3D dynamic liver imaging.", "It uses shifting k-space sampling patterns to reduce pixel aliasing and overlap."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "CAIPIRINHA is clearly a k-space (not image domain) PI technique, as it depends on k-space data sampling and manipulation prior to reconstruction."}}
{"id": "q_PIQUIZ_06", "question": "What happens to the imaging time in a PI study as the acceleration factor (R) is increased from 2 to 8?", "golden_answers": [0], "choices": ["It decreases by a factor of 4", "It decreases by a factor of 2", "It decreases by a factor of √2", "It decreases by a factor of 1/√2"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "Imaging time is inversely related to R, so if R quadruples (from 2 to 8), the imaging time is reduced by a factor of 4 Link to Q&A discussion"}}
{"id": "q_PIQUIZ_07", "question": "What happens to the signal-to-noise ratio (SNR) in a PI study as the acceleration factor (R) is increased from 2 to 8?", "golden_answers": [1], "choices": ["It decreases by a factor of 4", "It decreases by a factor of 2", "It decreases by a factor of √2", "It decreases by a factor of 1/√2"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "SNR is inversely related to √R, so if R quadruples (from 2 to 8), the SNR is reduced by a factor of √4 = 2."}}
{"id": "q_PIQUIZ_08", "question": "Which statement about the g-factor is false?", "golden_answers": [3], "choices": ["It depends on the number and location of coils.", "It depends on the direction of phase-encoding", "It varies by location across the image.", "Typical values range from about 10 to 100."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "The g-factor depends on 1) number and location of surface coils, 2) coil loading, 3) plane of imaging, 4) direction of phase-encoding within the scan plane, and 5) voxel location within the imaged region. With typical coil designs in common use, g-factors ranging from 1.0 to 2.0 across the imaging volume are commonly measured."}}
{"id": "q_PIQUIZ_09", "question": "The g-factor in the middle of a homogenous phantom imaged with PI is 2.0 while that near its periphery is 1.0. How do the SNR of the center and periphery compare?", "golden_answers": [0], "choices": ["SNR (center) is one-half as large as SNR (periphery).", "SNR (center) is equal to SNR (periphery).", "SNR (center) is twice as large as SNR (periphery).", "SNR (center) is four times as large as SNR (periphery)."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "SNR is inversely related to the g-factor, so if the g-factor doubles, the SNR is only ½ as large."}}
{"id": "q_PIQUIZ_10", "question": "Artifacts specific to parallel imaging include all of the following except", "golden_answers": [2], "choices": ["Coil sensitivity artifacts", "Fold-over (SENSE) ghosts", "Chemical shift", "Spatially dependent noise"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "Chemical shift artifacts are unaffected by the PI reconstruction process and are thus not unique."}}
{"id": "q_RAPIDQ_00", "question": "Fast/Turbo Spin-Echo Imaging methods are commercial applications of which original technique?", "golden_answers": [0], "choices": ["RARE", "MEDIUM", "ROAST", "SMASH"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Fast spin echo (FSE) imaging, also known as Turbo spin echo (TSE) imaging, are commercial implementations of the RARE (Rapid Acquisition with Relaxation Enhancement) technique originally described by Hennig et al in 1986."}}
{"id": "q_RAPIDQ_01", "question": "Which notation best describes the FSE/TSE technique?", "golden_answers": [1], "choices": ["90º−180º−echo−90º−180º−echo−90º−180º−echo−…..", "90º−180º−echo−180º−echo−180º−echo−180º−echo−…..", "90º−180º−echo−echo−echo−echo−…..", "90º−180º−echo−90º−echo−180º−echo−90º−echo−180º−echo−….."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "The FSE/TSE pulse sequence uses a series of 180º-refocusing pulses after a single 90º-pulse to generate a train of echoes."}}
{"id": "q_RAPIDQ_02", "question": "Advantages of FSE/TSE over conventional spin-echo imaging include all except", "golden_answers": [0], "choices": ["Decreased tissue energy deposition", "Reduced susceptibility artifacts", "Reduced imaging time", "Increased resolution or signal-to-noise in same imaging time"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "FSE/TSE offers significant reduction of imaging time by scanning multiple lines of k-space nearly simultaneously. This savings may be used to lengthen TR, allowing more time for recovery of longitudinal magnetization and hence improved signal-to-noise. A higher number of phase-encoding steps may be used, allowing improvement in spatial resolution. Susceptibility-induced signal losses are reduced. However, the multiple 180º deposit considerable energy in tissue, leading to high specific absorption rates (SARs)."}}
{"id": "q_RAPIDQ_03", "question": "What is the main conceptual structural difference between FSE/TSE and Multi-echo Conventional Spin Echo (multi-CSE) sequences?", "golden_answers": [2], "choices": ["The number of 90º-pulses within a TR interval", "The pattern of 90º- and 180º-RF pulses within a TR interval", "The pattern of phase-encoding gradients within a TR interval", "The pattern of frequency-encoding gradients within a TR interval"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "The FSE/TSE technique changes the phase-encoding gradient for each of these echoes (a multi-CSE sequence collects all echoes in a train with the same phase encoding)."}}
{"id": "q_RAPIDQ_04", "question": "What is the effective echo time (TEeff)?", "golden_answers": [3], "choices": ["The time between the 90º-pulse and first echo", "The time between the 90º-pulse and last echo", "The time between successive echoes in the train", "The time between the 90º-pulse and echo obtained at the center of k-space"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "The effective echo time (TEeff) is the time at which the central line of k-space (ky = 0) is being filled."}}
{"id": "q_RAPIDQ_05", "question": "What is the echo spacing (ESP)?", "golden_answers": [2], "choices": ["The time between the 90º-pulse and first 180º-pulse", "The time between the 90º-pulse and last echo", "The time between successive echoes in the train", "The time between the 90º-pulse and echo obtained at the center of k-space"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "The echo spacing is the time between any two successive echoes."}}
{"id": "q_RAPIDQ_06", "question": "What is the echo train length (ETL) or turbo factor (TF)?", "golden_answers": [0], "choices": ["The number of echoes in a TR interval", "The time between echoes in a TR interval", "The number of RF pulses in a TR interval", "The number of RF pulses required to reach the center of k-space"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "ETL or TF is simply the number of echoes in a FSE train between successive 90º-pulses. Imaging time is reduced proportionally by this factor."}}
{"id": "q_RAPIDQ_07", "question": "If a conventional spin-echo sequence with a certain TR/TE/spatial resolution takes 8 minutes to perform, an otherwise identical FSE sequence with an echo train length (turbo factor) of 8 would take how long?", "golden_answers": [0], "choices": ["1 minute", "2 minutes", "4 minutes", "8 minutes"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "With an ETL/TF = 8, 8 lines of k-space are transversed for each TR interval, reducing imaging time by a factor of 1/8."}}
{"id": "q_RAPIDQ_08", "question": "What image changes would not occur with increasing echo train length (ETL) or turbo factor (TF)?", "golden_answers": [1], "choices": ["Greater T2-weighting", "Increased signal-to-noise", "Spatial blurring", "Higher signal from fat"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Longer ETL's are associated with a decrease in overall signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) because the later echoes in the train are smaller in amplitude."}}
{"id": "q_RAPIDQ_09", "question": "What image changes would not be seen with increasing echo spacing (ESP)?", "golden_answers": [3], "choices": ["Increased motion artifacts", "Increased susceptibility artifacts", "Increased edge-related artifacts", "Increased signal-to-noise"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Increasing echo spacing (ESP) permits the use of longer TE's but adversely impacts SNR and CNR.  Motion, susceptibility, and edge-related artifacts increase.  In general, increased ESP has predominantly deleterious consequences on image quality; the shortest permitted ESP should therefore be chosen in most applications Link to Q&A discussion"}}
{"id": "q_RAPIDQ_10", "question": "What is the reason fat looks brighter on FSE/TSE than on Conventional SE images?", "golden_answers": [1], "choices": ["FSE/TSE have more intrinsic T1-weighting", "Multiple FSE/TSE 180º-pulses disrupt J-coupling in fat molecules", "Rapid phase-encode gradient switching inf FSE/TSE disrupts diffusion of fatty acids", "It’s just a visual illusion; the absolute fat signal is unchanged."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Although several factors may contribute to the FSE \"bright fat\" phenomenon, the dominant mechanism is thought to be T2 prolongation secondary to disruption of J-coupling interactions that take normally place between adjacent fat protons."}}
{"id": "q_RAPIDQ_11", "question": "Comparing FSE/TSE and CSE, which statement is false?", "golden_answers": [0], "choices": ["FSE/TSE shows increased sensitivity to susceptibility changes.", "FSE/TSE demonstrates increased magnetization transfer effects.", "FSE/TSE demonstrates spatial blurring", "FSE/TSE demonstrates pseudo-edge enhancement"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 1.0, "hint": "FSE/TSE sequences are less sensitive to susceptibility changes, as the 180°-refocusing pulses occurring at very short intervals allow relatively little time for susceptibility-induced dephasing."}}
{"id": "q_RAPIDQ_12", "question": "Which pulse would be considered a driven-equilibrium pulse if played at the end of an MR sequence?", "golden_answers": [2], "choices": ["+90º", "+180º", "−90º", "−180º"], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 3.0, "hint": "Driven equilibrium (DE), also known as fast recovery, is technique in which a −90º \"flip-back\" pulse is used to help restore longitudinal magnetization at the end of an MR sequence."}}
{"id": "q_RAPIDQ_13", "question": "Comparing the tissue energy deposition of RF-pulses, which is true?", "golden_answers": [3], "choices": ["Both 90º- and 180º-pulses deposit approximately the same energy", "A 180º-pulse deposits twice the energy as a 90º-pulse.", "A 180º-pulse deposits half the energy as a 90º-pulse.", "A 180º-pulse deposits four times the energy as a 90º-pulse."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Energy deposition from an RF-pulse is proportional to the square of the flip angle (α²). Thus, a 180°-pulse deposits 4x the energy of a 90°-pulse."}}
{"id": "q_RAPIDQ_14", "question": "Which pulse sequence feature is not commonly implemented as described in 3D-FSE sequences like CUBE/SPACE/VISTA?", "golden_answers": [1], "choices": ["Very short TE’s (2-4 ms)", "Medium length echo trains (Turbo factors 8-16)", "Reduced flip angles", "Partial Fourier imaging with zero-interpolation filling."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "3D-FSE sequences use extremely long echo trains, with perhaps 100-200 echoes. Other features include non-selective RF pulses, parallel imaging, and optimized k-space trajectories."}}
{"id": "q_RAPIDQ_15", "question": "Why is a zig-zag k-space trajectory commonly used for echo planar imaging instead of a consistent Cartesian (left to right) trajectory as in spin-echo imaging?", "golden_answers": [2], "choices": ["It offers better spatial resolution.", "It has fewer artifacts.", "It is faster to perform.", "It is done in the phase-encode direction rather than frequency-encode direction."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "The zig-zag trajectory is popular because it is easy to program and faster, as it doesn’t require rewinding the readout gradient back to −kmax after each echo. The spatial resolution is the same, and the zig-zag is prone to more artifacts, like Nyquist N/2 ghosts."}}
{"id": "q_RAPIDQ_16", "question": "All of the following statements about single-shot FSE (HASTE) are true except", "golden_answers": [0], "choices": ["Gradient echo signal generation is used for speed.", "The total number of echoes may exceed 200.", "Phase-conjugate symmetry is exploited to limit phase-encode steps.", "Common applications include MR cholangiography and MR myelography."], "metadata": {"subject": "K-space and Rapid Imaging Quiz", "level": 2.0, "hint": "Implicit in its name SS-FSE/HASTE is a fast-spin echo technique, meaning that spin-echoes, not gradient echoes are recorded."}}
{"id": "q_1_00", "question": "When the current flowing through a wire reverses direction, the magnetic field around the wire", "golden_answers": [3], "choices": ["Does not change", "Increases", "Disappears", "Reverses direction"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Ampère’s Law states that a current (i) in a wire induces a magnetic field (B) around the wire. if the direction of current flow reverses, the direction of the field does also, so d) is correct. The magnitude of the field depends on the magnitude of the current, so b) and c) are false. Link to Q&A discussion"}}
{"id": "q_1_01", "question": "The bulk magnetic properties of matter derive primarily from", "golden_answers": [2], "choices": ["Protons", "Neutrons", "Electrons", "Whole nuclei"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The combination of intrinsic electron spin and electron orbital angular momentum is primarily responsible for the bulk magnetic properties of matter. Protons, neutrons, and whole nuclei possess spin but the size of the magnetic effect is relatively small and limited to juxta-nuclear region of the atom only.  Link to Q&A discussion"}}
{"id": "q_1_02", "question": "If the current in a wire doubles, the induced magnetic field", "golden_answers": [0], "choices": ["Doubles", "Quadruples", "Remains the same", "Is reduced by half"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Ampère’s Law states that a current (i) in a wire induces a magnetic field (B) around the wire proportional to that current. If the current doubles, the magnitude of B also doubles. Link to Q&A discussion"}}
{"id": "q_1_03", "question": "The direction of magnetic field lines surrounding a wire can be determined using", "golden_answers": [0], "choices": ["The right-hand rule", "The left-hand rule", "Faraday's Law", "Lenz' Law"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Fleming developed the right hand rule in which if you grasp a wire carrying current with the right hand and point your thumb in the direction of the current, your fingers will curl around the wire in the direction of the induced magnetic field. Link to Q&A discussion"}}
{"id": "q_1_04", "question": "The voltage induced across a stationary conductor in an external static magnetic field", "golden_answers": [2], "choices": ["Depends on the angle of the conductor with the magnetic field", "Increases with time", "Is zero", "Depends on the strength of the magnetic field"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 3.0, "hint": "This is an example of the Faraday-Lenz Law, where the induced voltage is directly proportional to the rate of change of the magnetic field (dB/dt). In this case both the conductor and magnetic field are static, so dB/dt = 0 an the induced voltage is zero. Link to Q&A discussion"}}
{"id": "q_1_05", "question": "Concerning the relationship between electricity and magnetism, which of the following statements is false?", "golden_answers": [2], "choices": ["A constant current in a wire induces a constant magnetic field around the wire.", "A changing current in a wire induces a changing magnetic field around the wire.", "A constant magnetic field induces voltage in a nearby stationary wire.", "A changing magnetic field induces voltage in a nearby wire."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Ampère’s Law states that a current (i) in a wire induces a magnetic field (B) around the wire. If the current is constant, the magnetic field is constant, but if the current fluctuates, so will the magnetic field. Thus (a) and (b) are true."}}
{"id": "q_1_06", "question": "Which question about the Tesla (T) is correct?", "golden_answers": [3], "choices": ["It is the official unit for magnetic induction field strength in the cgs system.", "1 Tesla = 1,000 Gauss (G)", "1 G = 1 mT", "It is one of the coolest cars on the road"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "The Tesla is the unit for magnetic induction field strength in the International System of Units (SI), formerly known as the mks (meter-kilogram-second) system. Gauss is the equivalent unit in the cgs (centimeter-gram-second) system, so a) is false. 1 Tesla = 10,000 G, and 1 G = 0.1 mT, so both b) and c) are false. This leaves option d) as the correct answer, which everyone knows anyway! Link to Q&A discussion"}}
{"id": "q_1_07", "question": "Concerning magnetic field strengths, which statement is true?", "golden_answers": [0], "choices": ["The earth's magnetic field is about 0.5 G.", "A junkyard electromagnet that picks up cars is much stronger than the main field of most MR scanners.", "Research MR scanners for humans now exist with field strengths exceeding 20 T.", "Higher field strength scanners have wider bores than lower field strength scanners to accommodate the extra flux lines"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The earth’s magnetic field at the equator is about 0.5 G, so a) is the correct answer. Junkyard electromagnets generally have field strengths of about 1T, limited by the flux density of steel, so they are much weaker than most MR scanners, and thus b) is false. The largest current human scanners are 11.7T, so c) is false. Higher field strength scanners have smaller bores, not larger ones, so d) is false. Link to Q&A discussion"}}
{"id": "q_1_08", "question": "Which of the following materials is paramagnetic?", "golden_answers": [3], "choices": ["Water", "Fat", "Bone", "Air"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Most biological tissues (including water, fat, and bone) are weakly diamagnetic. Molecular O2 is paramagnetic, overwhelming the weak diamagnetism of the other components of air N2 and CO2. Link to Q&A discussion"}}
{"id": "q_1_09", "question": "A material that is weakly repulsed by a magnetic field is known as", "golden_answers": [1], "choices": ["Paramagnetic", "Diamagnetic", "Superparamagnetic", "Ferromagnetic"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Diamagnetic materials generate an internal polarization (J) that opposes the externally applied field, so b) is correct. The polarization of the other classes of materials is in the direction of the field and are attracted by the field. Link to Q&A discussion"}}
{"id": "q_1_10", "question": "Susceptibility (χ) is negative for materials that are", "golden_answers": [2], "choices": ["Paramagnetic", "Superparamagnetic", "Diamagnetic", "Ferromagnetic"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Susceptibility (χ) is negative when the internal polarization (J) points opposite to the main magnetic field (B). By definition, only diamagnetic materials have negative susceptibilities. Link to Q&A discussion"}}
{"id": "q_1_11", "question": "Ferromagnetic materials form magnetic ________ when arrays of electron spins become linked via quantum exchange interaction.", "golden_answers": [3], "choices": ["Flux lines", "Poles", "Vectors", "Domains"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 3.0, "hint": "Exchange interaction is a quantum effect in which unpaired electrons link together to form individual magnetic domains which behave as individual small \"magnets\". Link to Q&A discussion"}}
{"id": "q_1_12", "question": "Comparing superparamagnetic and ferromagnetic materials, which statement is false?", "golden_answers": [2], "choices": ["Ferromagnetism is usually more powerful than superparamagnetism.", "Ferromagnetism persists when the magnetizing field is removed.", "Superparamagnetism persists once the external field is removed.", "Superparamagnetism can be thought of as a single-domain particle."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Ferromagnetic materials retain memory (remenance) of prior magnetization, while superparamagnetic particles are single domain but whose magnetization disappears once the the magnetizing field is removed. Link to Q&A discussion"}}
{"id": "q_2_00", "question": "The most common design configuration for clinical MR scanners is", "golden_answers": [1], "choices": ["Open bore superconducting", "Closed bore superconducting", "Open bore permanent", "Dipolar electromagnet"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Over 90% of MR scanners sold today are of the closed bore (cylindrical) superconducting type. The second most common is open bore permanent."}}
{"id": "q_2_01", "question": "The highest field strength permitted for adults in routine clinical practice by the United States Food and Drug Administration (FDA) is", "golden_answers": [2], "choices": ["3.0 Tesla", "7.0 Tesla", "8.0 Tesla", "11.7 Tesla"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The current FDA limit for clinical MR scanners is 8.0 T for adults and children older than 1 month; it is 4.0 T for children younger than 1 month. The highest field strength clinical scanner commercially manufactured are 7.0 T, although human-sized research scanners of up to 11.7 T exist. Link to Q&A discussion"}}
{"id": "q_2_02", "question": "The first company to produce a clinical whole-body MRI scanner for commercial use was", "golden_answers": [1], "choices": ["GE", "Fonar", "Siemens", "Technicare"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Raymond Damadian formed the first company FONAR to manufacture MR scanners for clinical use in 1982."}}
{"id": "q_2_03", "question": "The direction of the main magnetic field (Bo) in a cylindrical closed bore scanner is", "golden_answers": [0], "choices": ["Longitudinal (along the main axis) of the cylinder", "Horizontal (cross-wise to the cylinder and parallel to the floor)", "Vertical (cross-wise to the cylinder and perpendicular to the floor)", "Can be at any angle depending on which gradients are turned on"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The main magnetic field of cylindrical scanners is along the long axis of the cylinder (solenoid). Answer d) is patently false as gradients do not alter the direction of the (Bo) field."}}
{"id": "q_2_04", "question": "Which of the following is not an advantage of low- and intermediate-field (< 1.0 T) MR scanners?", "golden_answers": [2], "choices": ["Lower price", "Lower fringe field", "Improved detection of gadolinium enhancement", "Lower energy deposition in tissues"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Gadolinium enhancement relative to tissues is reduced at lower fields, a disadvantage."}}
{"id": "q_2_05", "question": "Which of the following is not an advantage of high-field (≥ 1.0 T) MR scanners?", "golden_answers": [2], "choices": ["Higher signal-to-noise", "Better detection of calcifications and hemorrhage", "Smaller artifacts around metallic implants", "Better magnetic field homogeneity"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Susceptibility artifacts around metal objects are worse at high fields than at lower fields."}}
{"id": "q_2_06", "question": "Quoted specifications for four different magnets are given below. Which one has the best homogeneity?", "golden_answers": [0], "choices": ["<1 ppm over a 40 cm DSV", "<1 ppm over a 20 cm DSV", ">1 ppm over a 40 cm DSV", ">1 ppm over a 20 cm DSV"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 3.0, "hint": "Homogeneity specifications are typically quoted as magnetic field deviation in parts per million (ppm) over a defined spherical volume (DSV). So a magnet with the smallest ppm over the largest DSV would be the most homogeneous — answer a). Link to Q&A discussion"}}
{"id": "q_2_08", "question": "Which of the following statements about passive shimming is true?", "golden_answers": [2], "choices": ["Its primary purpose is to correct for field distortions produced by a patient's body.", "Ferromagnetic materials cannot be used for passive shimming.", "Passive shimming is affected by room temperature.", "Once the field is calibrated and magnetic homogeneity achieved, the passive shim materials can be removed."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Passive shimming involves the placement of ferromagnetic elements (typically plates or rods to correct for static field inhomogeneities in an empty magnet, not one containing a patient. Thus a) and b) are both false. The shim elements are made of metal and hence the quality of shimming depends upon scanner and room temperature, so answer c) is true.  The shim elements are not removed, but remain in the magnet after shimming is completed, so d) is false. Link to Q&A discussion"}}
{"id": "q_2_09", "question": "Which of the following statements about superconductivity is correct?", "golden_answers": [2], "choices": ["All elements can become superconducting if the temperature is low enough.", "Only metals can become superconductors.", "The magnetic field is zero inside the center of a superconducting wire.", "The resistance of a wire linearly decreases toward zero as the temperature falls below the transition temperature (TC)."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Only about half of the known elements can become superconductive at low temperatures, so a) is incorrect. Most of these are metals or metal alloys, but some non-metal ceramics may also possess superconductivity. The onset of superconductivity is immediate, with resistance dropping to zero once the transition temperature is crossed; thus answer d) is false. The correct answer is c), which describes the Meissner effect, the complete expulsion of all magnetic fields from the interior of the superconductor with creation of a state of perfect diamagnetism."}}
{"id": "q_2_10", "question": "The superconducting component in the main windings of nearly all clinical MR scanners is an alloy of", "golden_answers": [0], "choices": ["Niobium (Nb) and Titanium (Ti)", "Niobium (Nb) and Copper (Cu)", "Nickel (Ni) and Titanium (Ti)", "Nickel (Ni) and Copper (Cu)"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "The main windings of nearly all clinical superconducting scanners use Niobium (Nb) - Titanium (Ti) alloy microfilaments embedded in a copper core. The copper core is not superconducting but serves to support the microfilaments and serve as a current shunt in the event of a quench."}}
{"id": "q_2_11", "question": "The cryostat of a typical superconducting MR scanner contains all of the following except", "golden_answers": [1], "choices": ["Liquid helium", "Liquid nitrogen", "Main magnet windings", "superconducting shim coils"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Although common in the past, modern refrigeration systems have obviated the need for liquid nitrogen, so only liquid helium is present within the cryostat of today's MR scanners."}}
{"id": "q_2_12", "question": "The temperature of liquid helium is approximately", "golden_answers": [0], "choices": ["4 °K", "0 °K", "−4 °K", "−400 °C"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The temperature of liquid helium used to cool the magnet main windings is just a few degrees above absolute zero, about 4 °K. This is several degrees less than the transition temperature needed to maintain superconductivity in the NbTi alloy wires. No temperature equal or below absolute zero (0 °K or −273.15 °C) is possible, so answers b), c) and d) are all false."}}
{"id": "q_2_13", "question": "MRI facilities often display a sign on the door that says: \"Warning! The magnet is always on.\" This sign would not strictly apply to a", "golden_answers": [0], "choices": ["Resistive magnet scanner", "Permanent magnet scanner", "Superconducting magnet scanner", "The sign is applicable to all types of scanners, always."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Only FONAR still make still makes a resistive (electromagnet-type) MR scanner for human use, which can be turned off when not in use.  All permanent magnet and superconductive scanners remain at full field strength at all times, however, so the sign applies to nearly all MR facilities. Link to Q&A discussion"}}
{"id": "q_2_14", "question": "Pushing the \"big red button\" near the door to a room housing an MRI scanner", "golden_answers": [1], "choices": ["Immediately opens the door even if scanning is in progress", "Initiates a controlled quench of the magnetic field", "Turns off all electric power to the scanner and room", "Calls emergency providers (911) and sounds an alarm"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The \"big red button\" is often labeled \"Magnet Stop\" or \"Emergency Run Down\" and when pressed, initiates a controlled quench of the magnetic field. It should be used only in a life-threatening emergency, such as a patient pinned in the scanner by a metal object."}}
{"id": "q_2_15", "question": "During a magnetic quench, why should patients and employees be evacuated from the scan room?", "golden_answers": [1], "choices": ["Even in small quantities gaseous helium causes burning and irritation to the eyes.", "Asphyxiation may occur.", "Severe frostbite would be likely.", "The released helium may catch fire or explode."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Helium is odorless and colorless, but can potentially fill the scanner room resulting in asphyxiation. Fortunately, quench pipes typically vent nearly all released helium out of the room so death from a quench has never occurred in a medical setting to my knowledge. Direct contact with liquid helium would cause burns, but a mist of helium gas would not likely cause eye injury or frostbite (although this could occur in theory with high concentrations of gas in the room). Link to Q&A discussion"}}
{"id": "q_3_00", "question": "Magnetic field gradients for imaging are typically measured in units of", "golden_answers": [0], "choices": ["Millitesla per meter (mT/m)", "Gauss per second (G/s)", "Tesla (T)", "Tesla per meter per second (T/m-s)"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "A magnetic field gradient is defined as the change in magnetic field measured over a certain distance, so the only appropriate unit is answer a), millitesla per meter= [magnetic field strength]/distance. Gradient strength is also reported in Gauss/cm (G/cm)."}}
{"id": "q_3_01", "question": "For a supine patient, enabling the z-gradient alone to alter the magnetic field within a patient during slice selection would create a(n)", "golden_answers": [0], "choices": ["Axial slice", "Coronal slice", "Sagittal slice", "Oblique slice"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Applying a single gradient causes a frequency variation of protons as a function of position along the direction of the gradient. This change in frequency can be used for spatial encoding. If the gradient is played out during slice selection and again during signal readout, a slice can be selected perpendicular to the gradient directio Link to Q&A discussion"}}
{"id": "q_3_02", "question": "What is the effect of applying the x- and z-gradients simultaneously during slice selection?", "golden_answers": [2], "choices": ["The image will be distorted.", "Significant interslice cross-talk will occur.", "An oblique slice will be created.", "The scanner will display a warning that such a combination is not allowed."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Applying a single gradient during slice selection creates a slice perpendicular to the axis of the gradient. Applying two (or three) gradients simultaneously produces single (or double) oblique slices respectively."}}
{"id": "q_3_03", "question": "When the y-gradient is turned on, what happens to the direction of the main (Bo) field?", "golden_answers": [3], "choices": ["The Bo field now points slightly to the right.", "The Bo field now points slightly toward the ceiling.", "The Bo field is reversed.", "The Bo field remains pointing in its original (z)-direction."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Gradients do NOT generate transverse components that rotate/tip Bo from side-to-side or up-and-down.  They act only to create in-plane \"skewing\" of the z-components of Bo."}}
{"id": "q_3_04", "question": "The basic coil configuration used to generate the z-gradient in a cylindrical MR scanner is known as", "golden_answers": [0], "choices": ["Maxwell pair.", "Double saddle.", "Golay.", "Fingerprint."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Z-gradients are typically produced using two looped coils carrying current in opposite directions, a configuration known as the Maxwell pair. The other coil types listed are used primarily for x- and y-gradients."}}
{"id": "q_3_05", "question": "Which of the following statements about eddy currents is false?", "golden_answers": [2], "choices": ["They create a wide range of image artifacts, including ghosts and blurring.", "They are a manifestation of Faraday's Law of induction.", "They especially affect traditional spin-echo sequences with long TE's.", "They create tissue heating."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Eddy currents are produced rapidly changing magnetic fields (especially from the switching of imaging gradients) and are thus a manifestation of Faraday's Law. They are typically seen with rapid gradient echo or echo-planar sequences using short TE's; hence answer c) is false. They are uniformly undesirable, creating various artifacts and tissue heating problems."}}
{"id": "q_3_06", "question": "Concerning actively shielded gradients, which statement is true?", "golden_answers": [3], "choices": ["The are the most effective way to reduce eddy currents in superconducting systems.", "The are the most effective way to reduce eddy currents in superconducting systems.", "Current in these coils runs in a direction opposite to their associated imaging gradients.", "All of the above are true."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Active shielded gradients are nearly universally used in superconducting scanners because of their high effectiveness in reducing eddy currents in the magnet itself. They do not affect eddy currents generated in tissues, however."}}
{"id": "q_3_07", "question": "Which of the following methods is not used to reduce eddy currents:", "golden_answers": [2], "choices": ["Actively shielded gradients.", "Self-shielded gradients.", "Active shimming coils.", "Pre-compensation."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "The terms “Actively shielded” and “self-shielded” gradients are synonymous, and are the most effective way to reduce eddy currents. Pre-compensation distortion of waveforms is also helpful. Active shimming coils are used to make the main magnetic field more homogeneous and have nothing to do with eddy currents or their correction."}}
{"id": "q_3_08", "question": "Typical values for peak gradient strength in a modern 1.5 T scanner are in the range of", "golden_answers": [1], "choices": ["1-10 mT/m.", "20-50 mT/m.", "200-400 mT/m.", "500-1000 mT/m."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Lower field strength permanent magnets have peak gradients in the range of 15-25 mT/m."}}
{"id": "q_3_09", "question": "The time for a gradient to ramp from zero to its maximum value is known as its", "golden_answers": [0], "choices": ["Rise time.", "Gradient time.", "Slew rate.", "Duty cycle."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "This is the definition of rise time."}}
{"id": "q_3_10", "question": "The definition of gradient slew rate is", "golden_answers": [2], "choices": ["Peak gradient strength ÷ main field strength (Bo).", "Peak gradient strength ÷ total time the gradient is on.", "Peak gradient strength ÷ Rise time.", "The number of times a gradient is turned on and off per second."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Slew rate is defined to be Peak gradient strength ÷ Rise time."}}
{"id": "q_3_11", "question": "The units for slew rate are given in", "golden_answers": [1], "choices": ["Millitesla per meter (mT/m).", "Tesla per meter per second (T/m/s).", "Tesla per second (T/s).", "Milliseconds (ms)."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Peak gradient strength is typically measured in mT/m and rise time is measured in ms. Their ratio, slew rate, therefore has units T/m/s."}}
{"id": "q_3_12", "question": "Typical maximum slew rate values quoted for modern 1.5 T scanners are in the range of", "golden_answers": [2], "choices": ["1−2 T/m/s.", "10−20 T/m/s.", "100−200 T/m/s.", "1000−2000 T/m/s."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 3.0, "hint": "Answer c) is correct. Slew rates much higher than this can be obtained in research scanners but are limited due to the risk of peripheral nerve stimulation by the rapidly switching gradients."}}
{"id": "q_3_13", "question": "A gradient that ramps from 0 to a peak amplitude of 30 mT/m in 0.25 ms has a slew rate of", "golden_answers": [3], "choices": ["30 T/m/s.", "60 T/m/s.", "90 T/m/s.", "120 T/m/s."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 3.0, "hint": "Slew rate = [Peak gradient strength] ÷ [Rise time] = [30 mT/m] ÷ [0.25 ms] = 120 T/m/s."}}
{"id": "q_3_14", "question": "Which gradient specification is generally the most important when assessing how well an MR system is capable of performing rapid, high-resolution imaging?", "golden_answers": [1], "choices": ["Peak gradient strength.", "Slew rate.", "Rise time.", "Magnetic field strength."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "The slew rate incorporates both peak gradient strength and rise time into its definition and is the best single gradient specification to consider. Static magnetic field strength is an important consideration for high-resolution imaging but is not a gradient specification."}}
{"id": "q_3_15", "question": "How many sets of paired physical gradients are present in an MR scanner?", "golden_answers": [2], "choices": ["1", "2", "3", "6"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Three sets of paired primary gradients are present in all MR scanners, producing field distortions along the three cardinal directions (x, y, and z).   Link to Q&A discussion"}}
{"id": "q_3_16", "question": "Which of the following statements about gradient duty cycle is false", "golden_answers": [3], "choices": ["It is commonly measured in percent (%).", "It represents the fraction of time that the gradient works at maximum amplitude.", "Its value depends on the pulse sequence timing parameters and number of slices.", "Its value is independent of the type of pulse sequence (SE, IR, etc)."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "The duty cycle is defined as the percent time a gradient works at maximum amplitude during a pulse sequence. Its value will therefore vary with the pulse sequence and timing parameters, so d) is false.  Link to Q&A discussion"}}
{"id": "q_3_17", "question": "Which of the following statements about the gradient subsystem is true", "golden_answers": [1], "choices": ["The gradient coils are located within the cryostat.", "Gradient coils generate considerable heat during operation.", "The gradient coils are cooled by liquid helium.", "Increasing power supplied to a gradient decreases the slope of the gradient."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Gradient systems are not superconducting and are not located within the cryostat. They do generate considerable heat and typically require water and air cooling (though not cooling by liquid helium). Increasing power to a gradient increases (rather than decreases) its strength/slope.  Link to Q&A discussion"}}
{"id": "q_4_00", "question": "Which coils are located closest to the patient in an MR scanner?", "golden_answers": [1], "choices": ["Gradient coils.", "RF-receiver coils.", "Shim coils.", "Body RF-transmit coils."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "RF-receiver coils are placed closest to the patient so they may detect the MR signal with highest sensitivity."}}
{"id": "q_4_01", "question": "In the construction of a superconducting MR magnet, which is the correct order of coils from outermost to innermost?", "golden_answers": [2], "choices": ["Main magnet windings, gradient coils, RF coils, shielding coils.", "Gradient coils, shield coils, main magnet windings, RF coils.", "Shielding coils, main magnet windings, gradient coils, RF coils.", "RF coils, shield coils, main magnet windings, gradient coils."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Shielding coils are the outermost coils. Their function is to reduce the external fringe fields from the main magnet windings, the next coil encountered. Next come resistive shim coils used to improve magnet homogeneity. Then the gradients, then the RF transmit coils, and finally the RF receiver coils (closest to the patient)."}}
{"id": "q_4_02", "question": "Although most local RF coils are \"receive only\", some specially designed to operate in \"transmit-receive (T/R)\" mode. T/R coils commonly offered by MR vendors include all of the following except", "golden_answers": [3], "choices": ["Head coils.", "Knee coils.", "Spectroscopy coils.", "Spine coils."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Standard spine and body phased surface coil arrays are not offered for transmit/receive dual operation."}}
{"id": "q_4_03", "question": "A 1.5 T MR scanner has a base operating frequency of approximately 64 MHz. In the electromagnetic spectrum, this is considered to be in the range of", "golden_answers": [1], "choices": ["Infrared frequencies.", "Radio frequencies.", "X-ray frequencies.", "Microwave frequencies."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "MRI operates in the same frequency range as those used for radio and TV transmission."}}
{"id": "q_4_04", "question": "Use of a single element surface coil placed directly on the patient offers which advantages?", "golden_answers": [0], "choices": ["High signal-to-noise.", "Increased depth of penetration.", "Capability for larger fields-of-view.", "All of the above."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "A single element surface coil offers high signal-to-noise for receiving signals from voxels beneath the coil. The depth of penetration is limited, however, usually to less than 75% of the diameter of the coil. Larger FOV's are not possible, limited again by the size of the coil."}}
{"id": "q_4_05", "question": "Comparing 10 cm and 20 cm diameter surface coils, which of the following is false?", "golden_answers": [2], "choices": ["The sensitive volume of the 20 cm coil is larger.", "The penetration depth of the 20 cm coil is greater.", "The 20 cm coil has higher signal-to-noise for voxels immediately under the coil.", "The 20 cm coil offers a larger field of view."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "For voxels immediately under the coil, the 10 cm coil would have superior SNR than for the 20 cm one.  The other statements are all true."}}
{"id": "q_4_06", "question": "Comparing linear and quadrature coils", "golden_answers": [2], "choices": ["Quadrature coils offer twice the signal-to-noise.", "Quadrature coils offer four times the signal-to-noise.", "Quadrature coils offer about 40% greater signal-to-noise.", "Quadrature coils are about 40% larger."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Quadrature coils can be the same size as linear coils, but offer a signal-to-noise ratio of approximately √2  (≈ 1.41), or about 40% greater than that of linear coils."}}
{"id": "q_4_07", "question": "A sinusoidal wave can be described by the equation S(t) = A sin (ωt − φ). The constant A represents", "golden_answers": [2], "choices": ["Angular frequency.", "Difference in height between positive and negative peaks.", "Half the difference in height between positive and negative peaks.", "Phase shift."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 3.0, "hint": "A is called the \"amplitude\" of the sinusoidal wave measured from zero to its maximum positive value. The full excursion between positive and negative peaks is 2A, so \"A\" is ½ this difference."}}
{"id": "q_4_08", "question": "An MR scanner employs three different magnetic fields— the main field (B0), gradient fields (G), and radiofrequency field (B1). In terms of relative strength from weakest to strongest, the proper ranking is", "golden_answers": [0], "choices": ["B1 < G < B0", "G < B0 < B1", "G < B1 < B0", "B1 < B0 < G"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 3.0, "hint": "The main magnetic field  (B0) is by far the strongest, typically larger than 1 Tesla. Gradient fields are of intermediate strength with values in the mT range. Radiofrequency fields are the smallest, with B1 values on the order of 10−50 μT."}}
{"id": "q_4_09", "question": "Which of the following is not an advantage of parallel (multi-)transmit RF?", "golden_answers": [2], "choices": ["Decreased RF-energy deposition in tissues.", "Reduced shading artifacts.", "Increased standing waves due to dielectric effect.", "More uniform excitation."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 3.0, "hint": "Parallel transmit RF excitation offers many advantages, particularly as field strength increases, including improved homogeneous excitation and artifact reduction. The incorrect answer a) standing waves due to dielectric effect are decreased, not increased with parallel transmission."}}
{"id": "q_4_10", "question": "Comparing phased array and parallel array coils, which of the following is true?", "golden_answers": [0], "choices": ["Both types of coils offer improved signal-to-noise and increased field-of-view.", "Overlap of coil elements is avoided in both types.", "Phased array coils are also known as switchable arrays.", "Both can be used equally well with parallel imaging acquisition methods."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Only answer a) is true. Overlap of coil elements is common design feature of phased array coil systems, but must be avoided in parallel arrays. Although some phased array coils are compatible with parallel imaging applications, most are not. Finally, phased and switchable arrays are not the same, the latter largely being abandoned 20+ years ago."}}
{"id": "q_4_11", "question": "Parallel imaging systems are composed of coil elements, segments, and channels. The proper transmission hierarchy beginning with the patient and proceeding upward through the processing chain is", "golden_answers": [1], "choices": ["Elements → channels → segments", "Elements → segments → channels", "Elements → channels → segments", "Channels → elements → channels"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Proper order is given above."}}
{"id": "q_4_12", "question": "Advantages of parallel receiver coil arrays include all of the following except", "golden_answers": [2], "choices": ["Increased signal-to-noise.", "Increased field-of-view.", "Ease of design.", "Reduced imaging time."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Parallel coil configurations offer all the advantages above, with the exception of ease of design. In fact, it is rather difficult to pack many small coils closely together in these arrays without significant magnetic interactions."}}
{"id": "q_4_13", "question": "The effective depth of penetration for signal reception from a 20 cm diameter single loop surface coil is approximately", "golden_answers": [0], "choices": ["10−15 cm", "20−25 cm", "30−40 cm", "40−50 cm"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "The penetration depth for reception from a simple loop RF surface coil is typically only about 50-75% of the coil's diameter.  Link to Q&A discussion"}}
{"id": "q_4_14", "question": "Concerning the main transmit RF-body coil, which statement is false?", "golden_answers": [0], "choices": ["It is commonly used to receive the MR signal", "It is built into the scanner gantry housing and cannot be seen by the patient", "It is considered a transceiver coil, capable of both RF transmission and reception.", "Its transmission field (B1) is perpendicular to the main magnetic field (B0)."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The body coil is hidden within the scanner gantry housing. Its primary purpose is to transmit the B1 field which is perpendicular to B0. It is a transceiver coil capable of both RF transmission and reception. However, it is seldom used for reception because better signal-to-noise is obtained using surface coils for this purpose. Hence, answer a) is false.   Link to Q&A discussion"}}
{"id": "q_5_00", "question": "Which of the following components of an MR system is typically not located in an adjoining equipment room?", "golden_answers": [3], "choices": ["RF-power amplifiers", "Gradient amplifiers", "Helium pump", "Gradient coils"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Gradient coils are an integral part of the MR scanner itself and are not located in a separate equipment room."}}
{"id": "q_5_01", "question": "Where is the master computer located that controls the MR scanner and processes data into images?", "golden_answers": [1], "choices": ["In the MR scanner room", "In the MR scanner control room", "In the nearby MR equipment room", "At least 25 meters distant from the main scanner to avoid interference"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The master computer is located at the scanner console in the control room immediately adjacent to the magnet room. Due to the shielding of the scanner, it does not need to be in a remote location (answer d is false). However, this is now starting to change and some commercial houses are starting to install it in the technical room."}}
{"id": "q_5_02", "question": "The function of the array processor is to", "golden_answers": [1], "choices": ["Generate triggers for the array of RF-pulses and gradient waveforms used for imaging", "Reconstruct the raw NMR data into images", "Calculate RF frequency offsets and gradient strengths for desired slice selection and field-of-view", "Activate and/or disable various coil elements in an array"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "The array processor is a special board within the main computer that operates the MR scanner. It is responsible for performing Fast Fourier Transformation (FFT) of the raw data and constructing the data into images."}}
{"id": "q_5_03", "question": "Which scanner is the heaviest (and would thus require the most floor support)?", "golden_answers": [0], "choices": ["0.35 T  Permanent magnet system", "0.6 T Resistive magnet system", "1.5 T Superconductive system", "3.0 T Superconductive system"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Permanent magnet systems may weigh over 35,000 pounds (16,000 kg), over 3 times more than a superconductive scanner."}}
{"id": "q_5_04", "question": "Which scanner is would have the lowest overall siting and operational costs?", "golden_answers": [0], "choices": ["0.35 T  Permanent magnet system", "0.6 T Resistive magnet system", "1.5 T Superconductive system", "3.0 T Superconductive system"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Notwithstanding additional siting costs regarding their weight as described in the previous question, permanent magnet scanners do not require cryogens nor a sophisticated chiller system, so their operational costs are extremely low. Their fringe fields are typically very small as well, allowing them to have much smaller room requirements. Resistive electromagnet scanners, by comparison, have high operational costs due to use of electricity and increased environmental cooling requirements. Superconducting scanners are the most expensive to site due to their size, fringe fields, and cooling requirements."}}
{"id": "q_5_05", "question": "Which component of a superconducting MR scanner does not require specialized cooling to maintain function?", "golden_answers": [3], "choices": ["Main coil windings", "Gradient coils", "Gradient amplifiers", "Radiofrequency coils"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The main coil windings, of course maintained at superconducting temperatures by liquid helium. Both gradient coils and amplifiers get very hot and must be cooled by circulating water/antifreeze exchanged through chiller circuitry. Radiofrequency amplifiers are usually in the same cabinet as gradients and also require air and/or water cooling. The RF transmit coils themselves do get warm but require no separate cooling. The RF receive coils close to the patient do not heat up at all."}}
{"id": "q_5_06", "question": "The B0 field of an MR scanner is most homogeneous at", "golden_answers": [2], "choices": ["At the opening (gantry) of the magnet", "At bore level about 1 meter directly in front of the magnet", "In the middle of the bore at isocenter", "On the outside of the magnet immediately against its wall"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The B0 field is most homogenous at magnet isocenter."}}
{"id": "q_5_07", "question": "Which scanner would have the largest fringe field?", "golden_answers": [3], "choices": ["0.35 T  Permanent magnet system", "0.6 T Resistive magnet system", "1.5 T Superconductive system", "3.0 T Superconductive system"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Fringe fields are generally directly related to field strength, so the higher the main field, the greater the fringe. Thus the correct answer is d). Magnet configuration also is important.  Specifically, C-shaped magnets (the typical configuration for permanent scanners) have relatively low fringe fields."}}
{"id": "q_5_08", "question": "If one moves from 1 meter to 2 meters away from a magnet, the fringe field will be reduced by a factor of approximately", "golden_answers": [3], "choices": ["√2", "2", "4", "8"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 3.0, "hint": "In theory the strength of a magnetic fringe field is inversely related to the third power of the distance (1/r³) from the magnet isocenter. Thus moving twice as far away from the magnet, the fringe field should fall by a factor of approximately 1/2³ = 1/8."}}
{"id": "q_5_09", "question": "The fringe fields of cylindrical superconducting magnet are highest", "golden_answers": [2], "choices": ["In the x-direction (transverse and horizontal to the axis bore)", "In the y-direction (transverse and vertical to the axis bore)", "In the z-direction (along the axis bore)", "They are equal in all directions"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Fringe fields are significantly higher along the z-axis (the direction of B0)."}}
{"id": "q_5_10", "question": "The primary purpose for passive magnetic shielding is", "golden_answers": [0], "choices": ["To reduce fringe magnetic fields outside the scanner room.", "To keep extraneous radiofrequency noise from entering the scanner room.", "To constrain the NMR signal to remain within the bore of the magnet for better reception.", "To reduce the effects of moving equipment (such as cars and elevators) from distorting the magnetic field."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Passive shielding typically involves placing iron posts or sheets of steel in selected places around scanner floor or wall to minimize fringe field extension outside the scanner room. Passive shielding is generally not necessary with modern self-shielded scanners unless they are closely space or near other sensitive equipment."}}
{"id": "q_5_11", "question": "Concerning passive shielding, which statement is true?", "golden_answers": [2], "choices": ["It is performed by placing heavy copper plates along the walls of the scanner room.", "It is a method to reduce extraneous radiofrequency interference with the MR signal.", "It is more commonly required for 7.0T than for 1.5 T installations.", "Active shielding technology found in modern scanner design has not changed the need for it."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Passive shielding is a method to reduce fringe magnetic fields, so a) copper lining of the walls to reduce b) RF-interference are incorrect. It is more needed for higher field strength installations, so c) is true. Active shielding technology in modern scanners has reduced the need for passive methods, so d) is false."}}
{"id": "q_5_12", "question": "Passive magnetic shielding of the scanner room is typically achieved using sheets or rods made of", "golden_answers": [1], "choices": ["Copper", "Iron", "Aluminum", "Lead"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "A ferromagnetic substance such as iron or steel is required to constrain the fringe field lines."}}
{"id": "q_5_13", "question": "The fringe magnetic field arising from an MR scanner", "golden_answers": [3], "choices": ["Can be eliminated by active shielding.", "Can be eliminated by passive shielding.", "Can be reduced by radiofrequency shielding.", "None of the above."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Active and passive shielding can reduce, but not eliminate fringe fields. Radiofrequency shielding reduces noise but does not affect fringe fields  Link to Q&A discussion"}}
{"id": "q_5_14", "question": "What is the “5 Gauss Line”?", "golden_answers": [2], "choices": ["A place inside the scanner where x- and y-gradients differ in strength by less than 5 Gauss (5 mT).", "The boundary in an MRI center inside of which one’s credit cards will be erased.", "A fringe field line that may pose danger to patients with certain pacemakers", "A fringe field line in the scanner room safe for patients but which MR technologists should avoid crossing."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The 5-Gauss Line was established by the US Food and Drug Administration (FDA) as a boundary to which the unsuspecting public should not be exposed. The value was based on the fact that the reed switch in older pacemakers could be flipped by exposure to this level of stray magnetic field, potentially converting a patient’s demand pacemaker into asynchrony mode. It should be recognized that it is not just a line, but a surface that extends outward from the scanner in 3 dimensions. Thus it can extend into the floors above and below the scanner as well as to the sides."}}
{"id": "q_5_15", "question": "Which statement about ACR Safety Zones 1 and 2 is correct?", "golden_answers": [0], "choices": ["Both Zones 1 and 2 lie outside the 5 Gauss line.", "Patient safety screening is required before entering Zone 2", "The general public should not be admitted to Zone 1; it is only for MR patients and their families.", "Patients with pacemakers can at risk if allowed to enter Zone 2."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Zone 1 is for the general public. Entry is generally restricted beginning in Zone 2, as this is where safety screening takes place. Both lie outside the 5 Gauss line and are safe for everyone."}}
{"id": "q_5_16", "question": "Which statement about ACR Safety Zone 3 is false?", "golden_answers": [1], "choices": ["Patients should not be admitted to Zone 3 unless they have undergone safety screening.", "Ferromagnetic objects may not be brought into this area.", "The MR operator's console is located in this area.", "Medical personnel should not be admitted to this area unless they have undergone MR safety training."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Zone 3 includes areas within the 5-Gauss line, so all patients and family members need to be screened prior to entry. Zone 3 includes the area where the MR operator's console is located. The fringe fields in Zone 3 are sufficiently small that there is no risk for flying ferromagnetic objects to be propelled into the scanner. Nevertheless, there is generally easy direct access from Zone 3 into the scanner room (Zone 4) where dangerous flying objects can occur. Ferromagnetic objects in Zone 3 are discouraged but not forbidden; they certainly should not be brought near the door of the scanner room. For these reasons all medical personnel must be trained/educated in MR safety before being allowed into Zone 3."}}
{"id": "q_5_17", "question": "Which statement about ACR Safety Zone 4 is true?", "golden_answers": [1], "choices": ["Accompanying family members should never be allowed access to Zone 4.", "Zone 4 is synonymous with the room containing the MR scanner.", "Zone 4 is includes the scanner, the operator's console, and equipment room (where gradient amplifiers are located).", "A locked door requiring badge, key, or combination access must be present and remain closed between Zone 3 and Zone 4 except when moving patients."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Zone 4 is the scanner room itself, so b) is true and c) is false. Family members may be allowed in the scanner room provided they have been appropriately screened, so a) is false. The door to the scanner room is not locked and is frequently left open when scanning is not in progress (though we recommend having a strap across it to prevent inadvertent entry). Ferromagnetic materials should not be brought into Zone 4 as the risk of them being propelled into the scanner is high."}}
{"id": "q_5_18", "question": "Why might large trucks on a road 20 meters away from an MR scanner be of potential concern for siting?", "golden_answers": [2], "choices": ["Their CB radios operate at the same frequencies as the MR signal.", "The scanner magnetic field can be affected by the dense iron in their chassis as they pass by.", "The physical vibrations they produce can affect image quality.", "At this distance heavy truck traffic should be of no concern at all."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Environmental vibrations can significantly affect scanner performance, and sites should undergo vibration testing prior to installation of a scanner. The frequent passage of heavy trucks on a nearby road would be one possible cause. Other vibration sources include nearby air conditioning equipment, motors, and building elevators. RF-interference from CB radios should not be a special problem, as these frequencies would normally be filtered out by standard RF-shielding. At a distance of 20 meters, moving metal should not cause a static field disturbance; however, this could be of concern if the trucks passed as close as 10 meters by."}}
{"id": "q_5_19", "question": "The loud noise produced by an MR system during a scan is primarily due to", "golden_answers": [0], "choices": ["Vibrations of the gradient coils", "Vibrations of the radiofrequency coils", "Vibrations of the main magnet windings", "Vibrations from the chiller and helium pump"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "The noise produced during a scan is primarily due to electromechanical vibrations generated by gradients as they are rapidly turned on and off during a pulse sequence. This is transmitted to other structures in the magnet housing that may also vibrate secondarily and amplify the noise."}}
{"id": "q_5_20", "question": "Which of the following sequences would likely generate the loudest noise during scanning?", "golden_answers": [2], "choices": ["T2-weighted Turbo spin-echo (TSE) imaging of the spine", "Dixon fat-water imaging of the liver", "Echo-planar diffusion tensor imaging of the brain", "MR spectroscopy of the prostate"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "The loudest sequences are those where gradients are switched on and off most rapidly, such as in echo-planar imaging and short TE gradient echo imaging."}}
{"id": "q_5_21", "question": "Which of the following statements about MR scanner noise is false", "golden_answers": [1], "choices": ["Sound levels can reach up to 120 dB for some sequences.", "Although potentially uncomfortable for the patient, there is no real risk to hearing.", "Ear protection is mandatory for all patients undergoing MR imaging.", "New quiet pulse sequences can reduce noise levels to within 10 dB of background."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "Sound levels indeed can reach 120 dB for some sequences, especially echo-planar ones. This can result in damage to the inner ear and produce hearing loss, so option b) is false. Thus ear protection is mandatory for all patients."}}
{"id": "q_5_22", "question": "Which of the following methods can reduce scanner noise?", "golden_answers": [3], "choices": ["Avoidance of echo-planar sequences", "Use of \"soft\" gradient pulses with longer rise times", "Use of 3D ultrashort TE sequences", "All of the above"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "These strategies will all produce a reduction of noise levels during scanning."}}
{"id": "q_5_23", "question": "Newer \"quiet\" MR sequences with longer gradient ramp times are now available. Which of the following statements about these sequences is true", "golden_answers": [0], "choices": ["They can reduce noise levels to within 10 dB of background.", "This strategy can be applied to all pulse sequences.", "They can be employed with no signal-to-noise penalty.", "They do not affect number of slices for a given TR."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Newer quiet sequences can reduce noise levels to less than 10 dB of background, so answer a) is true. They can be used on many (but not all) pulse sequences. Because of the increasing rise and fall times there is a shorter sampling window and SNR is reduced. A penalty in the maximum number of slices may also occur at constant bandwidth due to the increased time spent in ramping gradients."}}
{"id": "q_5_24", "question": "Radiofrequency shielding of the scanner room is most commonly achieved by lining the walls with thin sheets of", "golden_answers": [2], "choices": ["Iron", "Aluminum", "Copper", "Lead"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "A thin layer of copper around the entire room is most commonly used in scanner installations. It acts as a Faraday cage and is effective at reducing penetration of extraneous radiofrequencies. However, virtually any conductive metal could be used for this purpose, and both steel and aluminum cages are occasionally used. Link to Q&A discussion"}}
{"id": "q_5_25", "question": "The primary purpose for radiofrequency shielding is", "golden_answers": [2], "choices": ["To confine fringe fields to the scanner room itself.", "To constrain the NMR signal to remain within the bore of the magnet for better reception", "To keep extraneous radiofrequency noise from entering the scanner room", "To reduce the effects of moving equipment (such as cars and elevators) from distorting the magnetic field."], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 1.0, "hint": "RF-shielding primarily prevents extraneous radiofrequency noises from outside the scanner room from entering and contaminating the MR signal."}}
{"id": "q_5_27", "question": "A device that allows a plastic oxygen hose to be passed through the wall of an MR scanner room without disrupting the integrity of the RF-shielding is called a", "golden_answers": [2], "choices": ["Penetration panel", "Bandstop filter", "Waveguide", "Faraday cage"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "The correct answer is waveguide (c). This looks like a pipe mounted within the wall and has a design that it blocks/traps radiofrequencies in the Larmor frequency range from passing through. This device is commonly part of the penetration panel, which also includes bandstop filters for wires. The Faraday cage is the entire enclosure around a scanner room to produce RF shielding."}}
{"id": "q_5_28", "question": "A common location for RF-leakage into the scanner room is", "golden_answers": [0], "choices": ["Around the door", "Along seals of the scanner window", "At the penetration panel", "Along the junction of copper plates in the scanner room’s walls"], "metadata": {"subject": "Magnets & Scanners Quiz", "level": 2.0, "hint": "Because of repetitive opening and closing, RF-seals around the door are frequently damaged and a common source of RF-leakage into the room."}}
{"id": "q_FEPEQUIZ_00", "question": "What are the units for angular frequency (ω)?", "golden_answers": [3], "choices": ["Hertz (Hz)", "Cycles per second (cps)", "Radians per cycle", "Radians per second"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "Angular frequency (ω), also known as radial or circular frequency, measures angular displacement per unit time. Its units are therefore degrees (or radians) per second."}}
{"id": "q_FEPEQUIZ_01", "question": "Approximately how many degrees are in one radian?", "golden_answers": [2], "choices": ["30.0º", "45.0º", "57.3º", "71.7º"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "By definition, 2π radians span the arc of one circle, or 360º. So 1 radian = 360/2π ≈ 57.3º"}}
{"id": "q_FEPEQUIZ_02", "question": "A 180º-pulse is sometimes expressed using radians as a", "golden_answers": [1], "choices": ["π/2-pulse", "π-pulse", "3π/2-pulse", "2π-pulse"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "A 180º-pulse is half a circle, or a π-pulse."}}
{"id": "q_FEPEQUIZ_03", "question": "As gradients are turned on and off, the angular frequency (ω) of a spin changes with time (t), expressed by the function ω(t).   The area under the graph of ω(t) vs t between two time points (A and B) represents", "golden_answers": [0], "choices": ["The spin’s accumulated phase shift between A and B", "The spin’s change in frequency between A and B", "The energy acquired by the spin between A and B", "The change in field strength experienced by the spin between A and B"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "The area under the ω(t) vs t curve represents the accumulated phase of the spin during a certain interval. From a unit perspective, frequency is measured in radians or degrees per second while time is measured in seconds, so their product [ω(t) x  t] will have units of radians (or degrees)."}}
{"id": "q_FEPEQUIZ_04", "question": "The MR signal information received by the RF-coil can be classified as", "golden_answers": [1], "choices": ["Frequency modulated", "Amplitude modulated", "Phase modulated", "Pulse modulated"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "MR signal information, typically encoded over a range of 50-100kHz, arrives at the receiver amplitude-modulated on the RF carrier wave (e.g. at 64 MHz). The first step in signal process is called demodulation, which removes the carrier."}}
{"id": "q_FEPEQUIZ_05", "question": "The real and imaginary components during of an MR signal in the I and Q channels of a receiver are measured at a specific time point to be 3.0 and 4.0 au (arbitrary units) respectively. What is the actual magnitude of the signal?", "golden_answers": [1], "choices": ["3.5 au", "5.0 au", "7.0 au", "12.0 au"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "The magnitude (M) = [Re² + Im²]½ = [3² + 4²]½  [25]½ = 5.0 au."}}
{"id": "q_FEPEQUIZ_06", "question": "Concerning Fourier representation of the MR signal, which of the following statements is false?", "golden_answers": [2], "choices": ["The Fourier expansion of a signal can be written in either trigonometric or exponential form.", "To represent any real signal exactly, an infinite number of frequency components must be included in its Fourier representation.", "The Fourier transformation converts a time-based signal into the frequency domain, but the change cannot be reversed.", "The Fourier series representation of an MR image is always cut short (truncated)."], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "All are true except for (c).  Fourier transformation is the mathematical procedure connecting a time domain signal, s(t), and its frequency domain representation, S(ω). The inverse Fourier transform converts S(ω) back to s(t)."}}
{"id": "q_FEPEQUIZ_07", "question": "The time domain signal, s(t), that corresponds to a uniform/rectangular band of frequencies in S(ω) is called a", "golden_answers": [1], "choices": ["Double exponential", "Sinc function", "Gaussian", "Lorentzian"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "The sinc function, sinc(t) = [sin t]/t, Fourier transforms into a uniform band of frequencies, such as those used to define a slice profile in conventional 2D MR imaging  Link to Q&A discussion"}}
{"id": "q_FEPEQUIZ_08", "question": "Which of the following scientists did not win the Nobel Prize for their work in NMR?", "golden_answers": [1], "choices": ["Felix Bloch", "Raymond Damadian", "Paul Lauterbur", "Peter Mansfield"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "Raymond Damadian did not win the Nobel Prize for his work and considered it a personal injustice. He placed full-page ads in several large world newspapers urging the Nobel committee to change their minds, which they never did."}}
{"id": "q_FEPEQUIZ_09", "question": "Which of the following is not a method for spatial localization of the MR signal?", "golden_answers": [3], "choices": ["Frequency encoding", "Phase encoding", "Location of receiver coils", "Amplitude modulation"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "Choice (d), amplitude modulation, refers to the shape of transmitted or received RF-pulses but is not by itself a method of spatial localization."}}
{"id": "q_FEPEQUIZ_10", "question": "Which of the following statements about frequency encoding is incorrect?", "golden_answers": [1], "choices": ["It commonly used for in-plane localization for 2D imaging.", "It is commonly used for slice selection in 3D imaging.", "Each voxel actually contains a range of frequencies, not just a single frequency.", "For most applications a linear frequency encoding gradient is desired."], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "All are correct except (b). Frequency encoding is commonly used for slice selection in 2D imaging, but phase encoding is typically used for slice selection in 3D."}}
{"id": "q_FEPEQUIZ_11", "question": "What is a typical total receiver bandwidth for a 1.5T MR scanner?", "golden_answers": [1], "choices": ["1 kHz", "50 kHz", "250 kHz", "500 kHz"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "Receiver bandwidth is an operator-selectable parameter, chosen by the technologist before the scan begins. Available values for total receiver BW range from about 5-100 kHz with 50kHz being typical."}}
{"id": "q_FEPEQUIZ_12", "question": "What is the width of a pixel in the frequency encoding direction if the field-of-view is 25.6 cm and 512 frequency-encoding steps are used?", "golden_answers": [0], "choices": ["0.5 mm", "1.0 mm", "2.0 mm", "5.0 mm"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "Pixel width = FOVf ÷ # frequency encode steps = 256 mm ÷ 512 = 0.5 mm."}}
{"id": "q_FEPEQUIZ_13", "question": "If 256 complex measurements of a digitized MR signal are sampled in a period of 5.12 ms, what is the dwell time?", "golden_answers": [2], "choices": ["5 μs", "10 μs", "20 μs", "200 μs"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "The dwell time is the interval between digitized samples. So if 256 samples were obtained over a 5.12 ms period, the dwell time would be 5.12 ms/256 = 20 μs."}}
{"id": "q_FEPEQUIZ_14", "question": "What is the total receiver bandwidth if the interval between digitized samples (dwell time) is 25 μs?", "golden_answers": [2], "choices": ["2,500 Hz", "25,000 Hz", "40,000 Hz", "50,000 Hz"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "Total receiver BW is the same as the digitization rate of the MR signal. In equation form, BW = 1/td = 1/(25 μs) = 40,000 Hz."}}
{"id": "q_FEPEQUIZ_15", "question": "In clinical MR imaging at 1.5T, what frequency range would be typical for setting the receiver to  “narrow bandwidth”?", "golden_answers": [1], "choices": ["1 – 5 kHz", "5 – 20 kHz", "50 – 52 kHz", "100 – 101 kHz"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "A typical range for narrow receiver bandwidth would be choice (b), 5 – 20 kHz."}}
{"id": "q_FEPEQUIZ_16", "question": "Which of the following statements about narrow bandwidth is incorrect?", "golden_answers": [0], "choices": ["Narrow BW implies reduced sampling time.", "Narrow BW increases signal-to-noise.", "Narrow BW accentuates chemical shift artifacts.", "Narrow BW accentuates susceptibility artifacts."], "metadata": {"subject": "Making an Image Quiz", "level": 1.0, "hint": "Option (a) is false. Bandwidth is inversely proportional to sampling time. A synonym for \"narrow bandwidth\" is therefore \"extended sampling time\"."}}
{"id": "q_FEPEQUIZ_17", "question": "Which of the following statements about transmitter bandwidth is true?", "golden_answers": [1], "choices": ["It is automatically determined once receiver bandwidth is specified.", "Transmitter BW per se is not directly adjusted by the technologist when specifying scan parameters.", "Typical values for transmit BW are 50-100 kHz.", "Most modern RF-pulses for 2D slice-select are sinc-shaped."], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "The transmit bandwidth is not usually user-adjustable, so choice (b) is true. Typical values are 1000-2000 Hz and are independent of receiver bandwidth. Simple sinc pulses are no longer used for slice select, being supplanted by more sophisticated designs using the SLR algorithm."}}
{"id": "q_FEPEQUIZ_18", "question": "Cross-talk can be reduced by all of the following methods except:", "golden_answers": [1], "choices": ["Increasing gaps between slices", "Increasing the strength of the slice-select gradient", "Performing slice interleaving", "Improving the RF slice profile"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "Increasing the strength of the slice-select gradient will only serve to produce thinner slices, not improve cross-talk."}}
{"id": "q_FEPEQUIZ_19", "question": "The earliest commercial version of simultaneous slice excitation (offered by GE in the 1990s) applicable to single-channel RF coils was called", "golden_answers": [0], "choices": ["Phase Offset MultiPlanar (POMP)", "MultiBand (MB)", "Simultaneous Multi-Slice (SMS)", "HyperBand (HB)"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "The historical precursor to modern MB/SMS methods was POMP (Phase Offset MultiPlanar) imaging. The POMP technique used a composite RF-pulse to simultaneously excite two slices, each of which were phase-encoded over only one-half of the total field-of-view (FOV). Phase alternation allowed the two slices to be separately reconstructed without overlap. Unlike SMS, POMP does not utilize parallel imaging technology and is hence applicable to single-channel RF coils."}}
{"id": "q_FEPEQUIZ_20", "question": "Which of the following statements about MultiBand/Simultaneous Multi-Slice imaging is false?", "golden_answers": [3], "choices": ["Use of parallel imaging arrays is required.", "Acceleration factors of 2-4 are typical.", "The slices must be widely spaced apart (2-3 cm).", "The technique imposes a significant penalty in terms of signal-to-noise."], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "MB uses coil encoding together with either gradient- or RF-encoding to resolve data along the slice-select (z)-axis. Because modern coil arrays typically have only a few coil elements in the z-direction, coil sensitivity differences along that axis are rather poor. Accordingly the simultaneously excited slices must be spaced widely apart (typically at least 25−30 mm). Unlike standard parallel imaging acceleration techniques, MB/SMS acceleration results in little to no penalty in signal-to-noise. (Option d is false). This is because neither the echo train length, number of phase-encoding steps, nor number of k-space samples has been reduced as occurs in conventional parallel imaging acceleration methods."}}
{"id": "q_FEPEQUIZ_21", "question": "What is the approximate in-plane pixel dimensions of a 25 x 25 cm FOV image acquired using 192 phase-encoding steps and 512 samples in the frequency direction", "golden_answers": [0], "choices": ["1.3 x 0.5 mm", "2.6 x 0.5 mm", "1.3 x 5.0 mm", "2.6 x 5.0 mm"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "The pixel width in the phase encode direction is 250 mm ÷ 192 ≈ 1.3 mm, while that in the frequency encode direction is 250 ÷ 512 ≈ 0.5 mm."}}
{"id": "q_FEPEQUIZ_22", "question": "Concerning 2D Fourier Transform imaging, which statement is false", "golden_answers": [1], "choices": ["The number of unique echo signals equals the number of phase-encoding steps.", "The phase shifts between successive echoes are multiples of 180º.", "For low-amplitude phase-encodings the MR signal is strong but provides little information about spatial detail.", "For high-amplitude phase-encodings the MR signal is weak and provides little information about image contrast."], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "Choice (b) is false. The phase shifts between the rows are not simple multiples of 180°, but vary from echo to echo depending on the size of the phase-encoding step. The number of echo signals acquired equals the number of phase encode steps, which is usually 192 or 256.  For low order phase-encodings, the MR signal is strong. The frequency projection approximates the general shape of the object but lacks edge definition.  The higher order phase encode steps have smaller MR signals but provide more information about spatial detail, such as the location of edges."}}
{"id": "q_FEPEQUIZ_23", "question": "Why is the phase-encode direction often chosen along the shortest anatomic dimension?", "golden_answers": [0], "choices": ["This reduces wrap-around artifact.", "This reduces flow-related artifact.", "This reduces artifacts from gross patient motion.", "It is a requirement for parallel imaging."], "metadata": {"subject": "Making an Image Quiz", "level": 1.0, "hint": "Wrap-around (also called aliasing) occurs when the size of the body part imaged exceeds the defined field-of-view (FOV) in the phase-encode direction. This causes anatomy outside the FOV to be folded in over the main part of the image. To avoid wrap-around the phase-encoding direction is usually chosen to be along the shortest anatomic dimension. Flow-related and other motion artifacts may be moved around by changing the phase-encode direction, but the best direction is based on the location and types of these artifacts, which may or may not be best along the shortest dimension.  For parallel imaging there may be some restrictions on possible phase-encode directions allowed, but setting phase-encode along the shortest axis is not necessarily required."}}
{"id": "q_SCQUCON_00", "question": "Which steps in setting up an MR scan are in the proper chronological order?", "golden_answers": [2], "choices": ["Set landmark → Perform prescan → Acquire localizer → Position slices", "Acquire localizer → Position slices → Set landmark → Perform prescan", "Set landmark → Acquire localizer → Position slices → Perform prescan", "Perform prescan → Acquire localizer → Set landmark → Position slices"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "Choice (c) shows the correct order."}}
{"id": "q_SCQUCON_01", "question": "Which process in the list below is not a part of automatic prescan?", "golden_answers": [0], "choices": ["Specific Absorption Rate (SAR) estimation", "Quick shimming", "Center frequency adjustment", "Transmitter gain adjustment"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "Specific Absorption Rate (SAR) is estimated by the scanner based on the patient’s body weight, pulse sequence, and pulse sequence parameters selected. This occurs before automatic prescan, allowing the operator to adjust parameters to keep SAR within established limits. Automatic prescan is essentially the last step before the actual scan begins."}}
{"id": "q_SCQUCON_02", "question": "In which of the following situations is manual shimming (in addition to prescan quick shimming) nearly always required?", "golden_answers": [1], "choices": ["Diffusion-weighted imaging", "MR Spectroscopy", "Fast-spin echo imaging", "Dixon fat-water imaging"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "Very detailed high-order shimming is mandatory for spectroscopy. Although spectroscopy shimming can be automated, the settings always require review and often tweaking by the MR technologist."}}
{"id": "q_SCQUCON_03", "question": "In which of the following situations is center frequency adjustment most critical?", "golden_answers": [3], "choices": ["When using spatial saturation pulses", "When using flow saturation pulses", "When using arterial spin labeling pulses", "When using fat saturation pulses"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "The center frequency may be set on water protons, fat protons, or some average of the two.  Accurate center frequency setting is particularly important when spectral fat saturation pulses are employed to make sure the fat peak is adequately suppressed."}}
{"id": "q_SCQUCON_04", "question": "What artifact will occur if the receiver attenuator value is set too low during prescan?", "golden_answers": [0], "choices": ["Data clipping", "Wrap around", "Ghosts", "Diffuse noise"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "If the attenuator value is set too low (i.e., receiver gain is set too high), then the signal will overload the analog-to-digital converter, and data clipping will occur. Since the largest peaks of the MR signal typically are the low order phase-encode steps at the center of k-space, data clipping interferes with image contrast. The result is an image with an \"eerie\" appearance"}}
{"id": "q_SCQUCON_05", "question": "What is the purpose of dummy cycles during prescan?", "golden_answers": [3], "choices": ["To adjust RF-voltage to achieve a perfect 90º-pulse", "To allow warm-up of the transmit and receive circuitry", "To optimally match coil impedance with that of the patient", "To allow steady state longitudinal and transverse magnetization to be established"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "Once RF-excitation begins, the longitudinal and transverse magnetizations need time to reach their steady-state values. During prescan the scanner plays out several cycles of the sequence without recording a signal. These are called dummy cycles, disabled, or discarded acquisitions (DDA). The precise number of dummy cycles depends on the TR and the sequence chosen. Only once the system is near equilibrium does data collection begin."}}
{"id": "q_SCQUCON_06", "question": "To sell an MR scanner in the United States, a company must receive what kind of premarket clearance from the Food and Drug Administration?", "golden_answers": [1], "choices": ["401(k)", "501(k)", "1099", "457(b)"], "metadata": {"subject": "Making an Image Quiz", "level": 4.0, "hint": "In the United States the Food and Drug Administration (FDA) has statutory authority to regulate the sale and use of MRI equipment. MRI scanners are considered Class II devices, meaning that they have the potential for human harm and require pre-market 501(k) clearance prior to marketing. The FDA has issued guidance documents with non-binding (but strongly suggested) criteria — including those related to hardware, software, performance, site planning, and safety — to attain this premarket approval. The other numbers are all IRS forms and investment accounts unrelated to MRI Link to Q&A discussion"}}
{"id": "q_SCQUCON_07", "question": "Which of the following organizations does not offer MRI accreditation in the United States?", "golden_answers": [1], "choices": ["American College of Radiology (ACR)", "Centers for Medicare & Medicaid Services (CMS)", "RadSite", "The Joint Commission (TJC)"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "In the US there are four MRI accrediting organizations that are currently sanctioned by the Centers for Medicare & Medicaid Services (CMS) – the American College of Radiology (ACR), the Intersocietal Accreditation Commission (IAC), The Joint Commission (TJC), and RadSite."}}
{"id": "q_SCQUCON_08", "question": "Which of the following quality control measurements must be performed at least weekly on an MR scanner?", "golden_answers": [0], "choices": ["Center frequency", "Magnetic field homogeneity", "Slice thickness accuracy", "Monitor resolution"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "Daily QC activities include visual inspection of all scanner hardware, the function of safety and communication devices, and general assessment of image quality including identification of artifacts. On at least a weekly basis, a special MR phantom is placed in the scanner and various measurements are made and recorded.  Such measurements include landmark accuracy (table position), center frequency, image uniformity, transmitter gain or attenuation, geometric distortion, spatial resolution, artifact evaluation, and signal-to-noise ratio. Other more sophisticated testing should be performed semiannually or yearly by a medical physicist."}}
{"id": "q_SCQUCON_09", "question": "The most common cause of geometric errors is", "golden_answers": [2], "choices": ["Warping of the MR phantom", "Abnormal RF-coil impedance", "Miscalibration of one or more imaging gradients", "Center frequency drift"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "The most common cause of geometric errors is miscalibration of one or more imaging gradients. Gradients tend to drift over time and require periodic re-calibration by service engineers. Occasionally the problem is caused by Bo inhomogeneity due to improper shim adjustments or an occult ferromagnetic object lodged in the scanner bore."}}
{"id": "q_SCQUCON_10", "question": "Detailed procedures and standards for the two most commonly used methods of measuring signal-to-noise in a phantom come from which organization?", "golden_answers": [0], "choices": ["The National Electrical Manufacturers Association (NEMA)", "The International Electrotechnical Commission (IEC)", "The International Commission on Non-Ionizing Radiation Protection (ICNIRP)", "The American Society for Testing and Materials (ASTM International)"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "The National Electrical Manufacturers Association (NEMA) provides detailed methods and standards for evaluating all types of electrical devices. Those relating specifically to MRI quality include how to measure signal-to-noise (MS 1, 6, & 9), geometric distortion (MS 2 & 12), and uniformity (MS 3)."}}
{"id": "q_SCQUCON_11", "question": "When complex-valued MR signal data is converted into a magnitude image, the noise statistics are best described using a", "golden_answers": [3], "choices": ["Gaussian (normal) distribution", "Poisson distribution", "Gamma distribution", "Rician distribution"], "metadata": {"subject": "Making an Image Quiz", "level": 3.0, "hint": "Because region-of-interest (ROI) measurements are typically made on magnitude-reconstructed images, some correction to the statistics must take place. Recall that \"raw\" MR data is a complex number with real and imaginary parts. When converted to a magnitude only image, the pixel values corresponding to noise are no longer Gaussian, but skewed into a so-called Rician distribution."}}
{"id": "q_SCQUCON_12", "question": "The section of an MR phantom consisting of closely spaced lines or holes containing material with strong difference in signal intensity from the background is used to measure", "golden_answers": [2], "choices": ["Low-contrast object detectability", "Geometric distortion", "High-contrast spatial resolution", "Image uniformity"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "The high-contrast portion of MR phantoms contains closely spaced lines, edges, or holes containing material with strong differences in signal intensity from background. Low-contrast resolution refers to the ability to identify small holes in the phantom with only slightly different relaxation times from background."}}
{"id": "q_SCQUCON_13", "question": "The section of an MR phantom consisting of triangular ramps or wedges oriented at a known angle is used to measure", "golden_answers": [0], "choices": ["Slice thickness", "Slice position", "Linear accuracy", "Low-contrast resolution"], "metadata": {"subject": "Making an Image Quiz", "level": 2.0, "hint": "The most common method to estimate slice thickness is to use a phantom containing triangular ramps or wedges whose surfaces are oriented at a known angle (θ) to the plane of the slice. When a slice passes through the ramp, it produces a stretched \"shadow\" image whose full width half maximum (FWHM) can be estimated."}}
{"id": "q_GDCLINQZ_00", "question": "The element gadolinium is part of which periodic table group?", "golden_answers": [0], "choices": ["Lanthanides", "Actinides", "Alkaline-earth metals", "Transition metals"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 1.0, "hint": "Gadolinium, element number 64, is located in the exact middle of the lanthanide series of rare-earth elements."}}
{"id": "q_GDCLINQZ_01", "question": "The paramagnetic properties of gadolinium that make it suitable for a contrast agent derive from its", "golden_answers": [2], "choices": ["Odd number of protons", "Odd number of protons and neutrons together", "Unpaired inner shell electrons", "Paired electrons in bonding orbitals"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Although all elements with odd numbers of nucleons possess nuclear paramagnetism, (responsible for the NMR phenomenon), this is extremely weak except in the immediate vicinity of the nucleus. Because electrons have the same spin (½) but a much smaller size than protons, their gyromagnetic ratios are 657 times larger, giving them powerful magnetic moments. It is unpaired inner shell electrons that give gadolinium its paramagnetic properties."}}
{"id": "q_GDCLINQZ_02", "question": "In its 4f shell, gadolinium has", "golden_answers": [1], "choices": ["4 unpaired electrons", "7 unpaired electrons", "4 paired and 3 unpaired electrons", "7 paired electrons"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "The 4f electron shell has seven available positions, each of which may potentially be occupied by a lone electron or an electron pair. According to Hund’s rule of maximum multiplicity, electrons will occupy each position singly before filling them in pairs. Gadolinium has seven electrons available to fill the 4f shell, and they are all unpaired."}}
{"id": "q_GDCLINQZ_03", "question": "How many of gadolinium’s unpaired 4f shell electrons participate in bonding/chelation when made into a contrast agent?", "golden_answers": [0], "choices": ["0", "1", "4", "7"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "None of gadolinium’s 4f shell electrons are directly involved in bonding, thus retaining its powerful paramagnetic properties when formulated as a contrast agent."}}
{"id": "q_GDCLINQZ_04", "question": "If gadolinium is chelated with a very large molecule (like albumin), what happens to its T1 relaxation time?", "golden_answers": [1], "choices": ["It remains unchanged", "It shortens", "It lengthens", "It becomes shorter than T2"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Smaller aqueous contrast agents (like Gd-DTPA) tumble too quickly to be highly efficient at T1 relaxation. If the contrast agent attaches to a very large molecule (such as albumin), its motion slows to a range much closer to the Larmor frequency and its T1 relaxation time shortens dramatically. Note that choice (d) is impossible, as T1 is always greater than or equal to T2."}}
{"id": "q_GDCLINQZ_05", "question": "Which of the following statements about inner sphere and outer sphere relaxation effects is false?", "golden_answers": [3], "choices": ["On a molecule-by-molecule basis, inner sphere relaxation is much more powerful than outer sphere relaxation.", "Inner sphere relaxation requires very close approach of a water molecules to the gadolinium metallic center.", "Although weaker on a per molecule basis, outer sphere effects are important because they involve larger numbers of water molecules.", "Most gadolinium contrast agents have multiple coordination sites available for inner sphere relaxation to take place."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "A consequence of its electron structure is that the Gd+3 ion typically exhibits nine coordination sites for bonding and chemical interactions. In all MR contrast agents now commercially available, a ligand group occupies eight of these sites while the ninth is available for transient bonding by a solvent water molecule for an inner sphere effect to occur. So choice (d) is false."}}
{"id": "q_GDCLINQZ_06", "question": "The T1- and T2-relaxivities of a contrast agent are given in what units?", "golden_answers": [0], "choices": ["L/mmol-s", "mmol/s", "L/mmol", "unitless"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "The relaxivity of an MR contrast agent reflects how the relaxation rates of a solution change as a function of concentration [C]. Since a contrast agent may affect the two relaxation rates (1/T1 and 1/T2) individually, there are two corresponding relaxivities, denoted r1 and r2.  By definition, 1/ΔT1 = r1 [C] and 1/ΔT2 = r2 [C]. Since ΔT1 and ΔT2 are given in seconds and [C] is measured in millimoles per liter, r1 and r2 have units of L/mmol-s."}}
{"id": "q_GDCLINQZ_07", "question": "In which of the following scenarios would the T2-shortening effects of gadolinium not be expected to be seen?", "golden_answers": [2], "choices": ["MR of the bladder", "MR arthography", "Late enhancement phase cardiac MRI", "MR venography"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "In routine MR imaging, the mild T2-shortening effects of low doses of gadolinium (which decrease signal intensity) are usually overwhelmed by the more dominant T1-shortening effects (which increase signal intensity) and are therefore not normally observed. When high concentrations of contrast are present, low-T2 effects may predominate. This is seen routinely in MRI of the urinary tract, occasionally in MR arthrograms and venograms (where high concentrations of gadolinium are injected directly into joints or vessels); and in the \"first pass\" of gadolinium contrast through the vascular system on dynamic contrast enhanced (DCE) studies or time-resolved MR angiography. It would not be seen in late phase imaging of the myocardium."}}
{"id": "q_GDCLINQZ_08", "question": "Concerning gadolinium enhancement as a function of field strength, which statement is true?", "golden_answers": [2], "choices": ["All currently used contrast agents demonstrate a slight increase in T1-relaxivity with increasing field strength.", "Contrast agents with lower T1 relaxivities (r1) values produce stronger  enhancement.", "The same dose of contrast will typically generate more enhancement at 1.5T than 0.5T.", "Lower doses of contrast agents are needed at low-field compared to high-field."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 1.0, "hint": "Only (c) is true. Because tissue T1 values increase while contrast agent relaxivities are about the same or decrease only slightly with increasing field strength, the net effect is an increase in relative contrast enhancement as field strength increases Link to Q&A discussion"}}
{"id": "q_GDCLINQZ_09", "question": "Why do magnetization-transfer preparation pulses increase the visibility of gadolinium enhancement?", "golden_answers": [1], "choices": ["They do not. This is a myth.", "They suppress the signal from background tissues.", "They shorten tissue T1.", "They interfere with gadolinium-water inner sphere relaxation."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Because gadolinium (Gd) enhancement is caused by a water-Gd ion interaction (not macromolecular cross-relaxation), MT pulses suppress the signal from background tissues and render Gd-enhanced areas more conspicuous."}}
{"id": "q_GDCLINQZ_10", "question": "The first commercially marketed gadolinium-based MR contrast agent was", "golden_answers": [1], "choices": ["Dotarem®", "Magnevist®", "MultiHance®", "Omniscan®"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Magnevist®, marketed by Berlex Imaging (and subsequently acquired by Bayer), first received FDA approval in 1988."}}
{"id": "q_GDCLINQZ_11", "question": "Which of the following agents is macrocyclic?", "golden_answers": [0], "choices": ["Dotarem®", "Magnevist®", "MultiHance®", "Omniscan®"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Dotarem®, along with ProHance® and Gadavist®, are all macrocyclic. The others are linear in structure."}}
{"id": "q_GDCLINQZ_12", "question": "Concerning gadoxetic acid constrast (Eovist®/Primovist®), which statement is false?", "golden_answers": [1], "choices": ["Transient dyspnea after injection occurs in about 10% of patients.", "At least 90% of the administered dose is taken up by hepatocytes.", "Elimination is by both biliary excretion and glomerular filtration.", "Hepatic uptake and enhancement is decreased when bilirubin levels are elevated."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Only about half of the administered dose is taken up by hepatocytes. The remainder behaves as other nonspecific extracelleular gadolinium contrast agents."}}
{"id": "q_GDCLINQZ_13", "question": "Although no longer in production, what was unique about the liver contrast agent Teslascan™ sold in the 1990s and early 2000s?", "golden_answers": [0], "choices": ["It was based on manganese.", "It was based on iron.", "It was based on copper.", "It was based on magnesium."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "To date the only manganese-based contrast agent ever approved for worldwide sales and clinical use was mangafodipir trisodium (Mn-DPDP), marketed in the 1990's under the tradename Teslascan™. Due to low sales, poor clinical performance, and concerns over toxicity, Teslascan™ was withdrawn from the US market in 2003 and from the EU in 2010."}}
{"id": "q_GDCLINQZ_14", "question": "And speaking of MR contrast agents no longer in production, what was unique about Ablavar®?", "golden_answers": [2], "choices": ["It was based on manganese.", "It was based on iron oxide.", "It attached to albumin and served as a blood pool agent.", "It was taken up by the reticuloendothelial system."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "Withdrawn as a product in 2017 by its manufacturer due to poor sales, Ablavar® had been designed specifically for vascular imaging. The drug underwent reversible bonding to plasma proteins (principally albumin) when injected into the blood, allowing it to be confined intravascularly for several hours."}}
{"id": "q_GDCLINQZ_15", "question": "Concerning superparamagnetic iron oxides (SPIOs) and ultra-small superparamagnetic iron oxides (US-SPIOs), which statement is false?", "golden_answers": [1], "choices": ["US-SPIOs may be injected intravascularly, intradermally, or subcutaneously.", "The larger SPIOs are especially useful for lymph node imaging.", "Their T1 and T2 relaxivities are 10-20 x greater than gadolinium contrast agents.", "Their accumulation in the liver, spleen, and bone marrow can be mistaken for hemochromatosis."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "Option (b) is false. The largest of these SPIO nanoparticles (50-100 nm) undergo rapid uptake by the liver. Smaller US-SPIO particles (5-50 nm), remain in the circulation and are cleared by lymphatics, draining into lymph nodes where they are captured and retained by macrophages/histiocytes (and potentially other sinus-lining endothelial cells)."}}
{"id": "q_GDCLINQZ_16", "question": "Concerning ferumoxytol (Feraheme®/Rienso®) which statement is false?", "golden_answers": [0], "choices": ["It is now sold and marketed worldwide as an MR contrast agent.", "It has a long intravascular half-life after intravenous injection, behaving as a blood pool agent.", "It reduces both T1 and T2 relaxation times of the tissues wherein it accumulates.", "It must be given diluted and by slow intravenous injection."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "Although ferumoxytol was originally developed as an MR contrast agent, it was instead marketed and approved for intravenous treatment of iron-deficiency anemia associated with chronic renal disease. It has not yet received indications for use as an MR contrast agent. It’s use in this form is considered “off label”."}}
{"id": "q_GDCLINQZ_17", "question": "Concerning bowel contrast materials, a large volume, water-based solution like VoLumen® would be classified as what type of contrast agent?", "golden_answers": [2], "choices": ["Positive", "Negative", "Biphasic", "Neutral"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "Biphasic contrast agents are all water-based, appearing dark on T1-weighted and bright on T2-weighted images. Biphasic enteric contrast agents like VoLumen® contain nonabsorbable additives (resins, polyethylene glycol, mannitol, sorbitol, or other sugar alcohols) that help draw in and retain intraluminal water."}}
{"id": "q_GDCLINQZ_18", "question": "Concerning bowel contrast materials, a suspension of magnetite-based particles like GastroMARK® (ferumoxsil) would be classified as what type of contrast agent?", "golden_answers": [1], "choices": ["Positive", "Negative", "Biphasic", "Neutral"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "Negative contrast agents are designed to make the intraluminal contents dark, especially on T2-weighted images. GastroMARK® causes a remarkable drop in signal within the bowel lumen on both T1 and T2-weighted images. The darkening on T1-weighted images allows visualization of mucosal enhancement."}}
{"id": "q_GDSAFEQZ_00", "question": "Compared to non-ionic iodine-based contrast agents, the frequency of acute adverse reactions to gadolinium-based contrast agents is", "golden_answers": [1], "choices": ["About the same", "Slightly less", "Slightly more", "Much more"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 1.0, "hint": "Compared to many other drugs gadolinium contrast agents possess a very low incidence (<2.5%) of acute adverse reactions, mostly minor. Such rates are not too much higher than those occurring during placebo injection of saline and are about one-third as common as reaction rates recorded with nonionic iodine-based contrast media."}}
{"id": "q_GDSAFEQZ_01", "question": "Considering gadolinium-based contrast agents as a whole, what is the approximate rate of severe allergic reaction (e.g., facial edema, bronchospasm, hypotension, arrhythmias, widespread uticaria) expected?", "golden_answers": [1], "choices": ["1 in 500 patients", "1 in 5000 patients", "1 in 50,000 patients", "1 in 500,000 patients"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Moderately severe hypersensitivity reactions (including bronchospasm, laryngospasm, facial edema, tachycardia, arrhythmias, or widespread urticaria) occur in about 1 in 5000 cases."}}
{"id": "q_GDSAFEQZ_02", "question": "Considering gadolinium-based contrast agents as a whole, what is the approximate risk of death from a severe allergic reaction?", "golden_answers": [2], "choices": ["1 in 4,000 patients", "1 in 40,000 patients", "1 in 400,000 patients", "1 in 4,000,000 patients"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Worldwide, a number of severe anaphylactoid reactions to gadolinium-based MR contrast agents, including death, have been reported. The incidence of severe reactions is about 1 in 20,000 and the risk of death about 1 in 400,000."}}
{"id": "q_GDSAFEQZ_03", "question": "Which one of the following rare reactions to gadolinium has not been reported?", "golden_answers": [0], "choices": ["Rhabdomyolysis", "Pancreatitis", "Encephalopathy", "Acute renal failure"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "To my knowledge, acute rhabdomyolysis has never occurred following gadolinium administration. The other three have been rarely reported."}}
{"id": "q_GDSAFEQZ_04", "question": "Comparing “true” anaphylaxis and “anaphylactoid” reactions to gadolinium contrast, which statement is correct?", "golden_answers": [2], "choices": ["They can be distinguished based on their clinical presentation.", "Both are IgE-mediated.", "Both cause release of vasoactive amines and inflammatory mediators from mast cells.", "Both are dose-related."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "True anaphylaxis is an IgE-mediated type 1 hypersensitivity reaction and is not dose-related. Anaphylactoid reactions have an identical clinical pattern to \"true\" anaphylaxis but are not IgE-mediated. The two cannot be distinguished clinically. Both cause the same effect on basophils and mast cells to release histamine and other contents."}}
{"id": "q_GDSAFEQZ_05", "question": "Which of the following statements about the clinical features of nephrogenic systemic fibrosis (NSF) is incorrect?", "golden_answers": [3], "choices": ["Nearly all reported cases have been in patients with severe renal disease or insufficiency.", "Skin thickening and joint contractures are characteristic.", "Involvement of the liver, lungs, muscles and heart also occurs.", "Although painful and disfiguring, the disease is seldom fatal."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Nephrogenic systemic fibrosis (NSF) is a rare, progressive, usually fatal disease characterized by skin thickening, painful joint contractures, and fibrosis of multiple organs including the lungs, liver, muscles, and heart. Nearly all documented cases have occurred in patients with chronic severe renal insufficiency who have received gadolinium contrast."}}
{"id": "q_GDSAFEQZ_06", "question": "Which one of the following gadolinium-based contrast agents is less likely than the others to be associated with NSF?", "golden_answers": [1], "choices": ["Magnevist®", "Dotarem®", "OpitMARK™", "Omniscan™"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Except for the macrocyclic agent Dotarem®, the other three agents are all linear in structure and have been associated with the greatest number of reported cases of NSF. These have been classified by the ACR as Group I agents, and are no longer advertised in the US and have been withdrawn from the market in many other countries."}}
{"id": "q_GDSAFEQZ_07", "question": "Which gadolinium-based contrast agents has to date not been associated with any nonconfounded cases of NSF?", "golden_answers": [3], "choices": ["Dotarem®", "ProHance®", "MultiHance®", "Eovist®"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "No cases of NSF have been reported with the newest gadolinium agent, Eovist® (gadoxetate). However, Eovist® is primarily intended for hepatic imaging and thus there is only limited worldwide experience with it compared to the more general purpose agents. Furthermore, Eovist® (and any future new contrast agents) are being given in an “NSF-conscious” era, where high doses of gadolinium are avoided and careful scrutiny of renal function is undertaken prior to contrast administration."}}
{"id": "q_GDSAFEQZ_08", "question": "Below what level of glomerular filtration rate (GFR) does the American Kidney Foundation consider Stage 3 (moderately reduced function) kidney disease?", "golden_answers": [1], "choices": ["90 mL/min/1.73 m²", "60 mL/min/1.73 m²", "30 mL/min/1.73 m²", "15 mL/min/1.73 m²"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 1.0, "hint": "Stage 3 chronic kidney disease is generally diagnosed for GFRs in the range of 30-60 mL/min/1.73 m². This is about half the normal kidney function level of 90 mL/min/1.73 m²."}}
{"id": "q_GDSAFEQZ_09", "question": "Which one of the following statements about the use of gadolinium in neonates and infants is false?", "golden_answers": [1], "choices": ["The half-life of gadolinium contrast in a normal newborn is at least 4 times longer than in an adult.", "The per kilogram dose of contrast should be lower than that in adults.", "Neonates have a lower renal excretion rate of gadolinium contrast than adults.", "No cases of NSF in neonates or infants have been reported."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 1.0, "hint": "Renal excretion rates aside, neonates have twice the volume of extracellular fluid than adults have in proportion to their body weights. Therefore, neonates and young infants who receive gadolinium contrast on a dose-per-kilogram basis will have blood gadolinium concentrations of only one-half that in adults after equilibration. This fact argues against using a lower dose per kilogram in infants than in adults, even though the serum half-life is prolonged.  Clinical experience by our group and others has demonstrated that the adult dose of gadolinium contrast (0.1 mmol/kg for most extracellular agents) is also appropriate in infants and children."}}
{"id": "q_GDSAFEQZ_10", "question": "Concerning the administration of gadolinium contrast to lactating women, which statement is false?", "golden_answers": [3], "choices": ["Peak excretion into breast milk occurs at about 50 minutes after injection.", "Only a tiny fraction (0.01%-0.04%) of the administered dose is excreted in breast milk.", "Only 1% of orally ingested contrast gadolinium contrast is absorbed by the infant.", "Current scientific evidence shows that breast feeding must be avoided for at least 24 hrs."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Because (b) and (c) are true, the dose entering the infant's circulation is extremely small (1/1,000,000 of the maternal dose) and the potential toxic effects are thought to be miniscule. Only out of an abundance of safety, many centers recommend (but do not require) suspending breast feeding for 24 hours after a gadolinium-enhanced MR study."}}
{"id": "q_GDSAFEQZ_11", "question": "Concerning the administration of gadolinium contrast during pregnancy, which statement is false?", "golden_answers": [0], "choices": ["An increased number of congenital malformations have been observed in infants of mothers receiving gadolinium contrast during pregnancy.", "Gadolinium contrast easily passes through the placenta and into the fetal circulation.", "Gadolinium contrast absorbed by the fetus is excreted into the urine and subsequently into the amniotic fluid.", "Some gadolinium contrast in the amniotic fluid will be swallowed and resorbed through the fetal GI tract."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "In the only controlled human study to date of MRI and gadolinium exposure in pregnancy, a slightly higher incidence of stillbirths and early neonatal deaths (but not congenital malformations) was observed in the gadolinium-exposed group.  More worrisome, however, was an increased number of rheumatologic, inflammatory, and infiltrative skin conditions, including some resembling nephrogenic systemic fibrosis (NSF)."}}
{"id": "q_GDSAFEQZ_12", "question": "Which of the following statements concerning gadolinium deposition in the brain is false?", "golden_answers": [2], "choices": ["Accumulation occurs primarily in the basal ganglia, brainstem, and dentate nuclei.", "Several exposures are usually necessary before visible changes are seen.", "Changes are most visible on T2*-weighted images.", "The incidence of accumulation is less with macrocyclic contrast agents than linear ones."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "All are true except (b). High signal due to accumulated gadolinium is noted on T1-weighted images."}}
{"id": "q_GDSAFEQZ_13", "question": "Concerning “gadolinium deposition disease” which statement is false?", "golden_answers": [1], "choices": ["The FDA has determined there is no convincing current evidence for this diagnosis.", "One important piece of clinical evidence for it is the increased incidence of Parkinson’s disease in patients receiving gadolinium contrast.", "No tissue injury or morphologic changes in gadolinium-accumulating brain areas can be detected by microscopy.", "Celebrity Chuck Norris withdrew his lawsuit against Bracco where he claimed they “poisoned” his wife with gadolinium."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "The incidence of Parkinson’s disease is not increased in patients who received gadolinium contrast."}}
{"id": "q_HEMQUIZ_00", "question": "How many iron atoms are in a hemoglobin molecule?", "golden_answers": [3], "choices": ["1", "2", "3", "4"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "Hemoglobin is comprised of four subunits, each containing a heme group with an iron (Fe) atom nestled at its center."}}
{"id": "q_HEMQUIZ_01", "question": "How many sites on each heme group are available for binding oxygen or another small molecule?", "golden_answers": [0], "choices": ["1", "2", "3", "4"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "The Fe center of each heme group has 6 potential coordination sites, four of which are occupied by porphyrin nitrogens (N). The fifth coordination site (below the plane of the ring) covalently bonds with a histidine (His) residue from the F8 position of its respective globin chain. This leaves one free coordination site to which oxygen and other small molecules may transiently bind."}}
{"id": "q_HEMQUIZ_03", "question": "Which one of the hemoglobin derivatives listed below is diamagnetic?", "golden_answers": [0], "choices": ["Oxyhemoglobin", "Deoxyhemoglobin", "Methemoglobin", "Ferritin"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 1.0, "hint": "Oxyhemoglobin has no unpaired electrons and is therefore diamagnetic."}}
{"id": "q_HEMQUIZ_04", "question": "In arterial blood from a healthy patient, what is the expected proportion of deoxyhemoglobin?", "golden_answers": [1], "choices": ["0 %", "Less than 5%", "10 – 20 %", "Greater than 25 %"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "In arterial blood, the fraction of oxyhemoglobin is about 95%, while deoxyhemoglobin constitutes less than 5% (but not zero). A tiny amount of methemoglobin (<< 1%) may also be detected."}}
{"id": "q_HEMQUIZ_05", "question": "In venous blood from a healthy patient, what is the expected proportion of deoxyhemoglobin?", "golden_answers": [3], "choices": ["0 %", "Less than 5%", "10 – 20 %", "Greater than 25 %"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "In venous blood, oxy-Hb still predominates, though in a smaller ratio (venous oxy:deoxy ≈ 70:30.)"}}
{"id": "q_HEMQUIZ_06", "question": "Which of the following effects on the MR signal does not result from local increased hematocrit during blood clotting?", "golden_answers": [2], "choices": ["Decreased free water content, reducing T1, T2, and spin density.", "Decreased extracellular space, restricting diffusion.", "Increased concentration of phospholipids in red blood cell membranes, shortening T1.", "Increased concentration of hemoglobin, potentiating T2/T2* effects as transition to deoxy-hemoglobin occurs."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "All are true except (c). Phospholipid cell membranes have ultrashort T2 values and do not generate a fatty signal on MRI."}}
{"id": "q_HEMQUIZ_07", "question": "Which of the following imaging findings at 1.5T would not be expected to be seen in a hyperacute (< 12 hrs old) cerebral hematoma?", "golden_answers": [2], "choices": ["Restricted diffusion", "T1 signal isointense to brain", "T2 signal moderately hypointense to brain", "At least a rim of hypointensity on GRE/SWI images"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "In a hyperacute hematoma, oxyhemoglobin still predominates, except perhaps at the periphery, and the imaging findings suggest a relatively high-water content lesion that is moderately hyperintense on T2-weighted images."}}
{"id": "q_HEMQUIZ_08", "question": "Which of the following imaging findings at 1.5T would not be expected to be seen in an acute (12–48 hrs old) cerebral hematoma?", "golden_answers": [1], "choices": ["Restricted diffusion", "T1 signal hyperintense to brain", "T2 signal markedly hypointense to brain", "GRE/SWI images hypointense to brain"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "This phase of hematoma formation is dominated by intracellular deoxyhemoglobin, which shortens T2/T2* significantly. The hematoma becomes markedly hypointense on T2-weighted images."}}
{"id": "q_HEMQUIZ_09", "question": "Which of the following imaging findings at 1.5T would not be expected to be seen in an early subacute (2 days – 1 week old) cerebral hematoma?", "golden_answers": [2], "choices": ["Restricted diffusion", "T1 signal hyperintense to brain", "T2 signal hyperintense to brain", "GRE/SWI images hypointense to brain"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "This is the phase of hematoma formation where intracellular methemoglobin predominates. This hemoglobin derivative is highly paramagnetic. Because it is still contained within red blood cells, T2/T2* shortening effects still occur, so T2 signal is low, not high. Access of water molecules close to the iron center due to a conformational change in the globin moiety result in T1 shortening and a bright T1 signal."}}
{"id": "q_HEMQUIZ_10", "question": "Which of the following imaging findings at 1.5T would not be expected to be seen in a late subacute (1 week – 2 months old) cerebral hematoma?", "golden_answers": [1], "choices": ["Minimal to no restricted diffusion", "T1 signal hypointense to brain", "T2 signal hyperintense to brain", "GRE/SWI images show central hyperintensity"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "This phase of hematoma formation is dominated by extracellular methemoglobin, released from red blood cells that have ruptured. Methemoglobin is no longer concentrated into multiple intracellular compartments, but becomes uniformly dispersed throughout the hematoma cavity that is now bright on both T1- and T2-weighted images."}}
{"id": "q_HEMQUIZ_11", "question": "Which of the following imaging findings at 1.5T would not be expected to be seen in the center of a chronic (> 2 months old) cerebral hematoma?", "golden_answers": [3], "choices": ["Minimal to no restricted diffusion", "T1 signal hypointense to brain", "T2 signal hyperintense to brain", "GRE/SWI central hypointensity to brain"], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "The imaging characteristics of the center of a chronic hematoma reflects its high water content. As such this region is typically hyperintense to brain on T2-weighted images and hypointense on T1-weighted images with no or minimally restricted diffusion. GRE/SWI signal centrally is also high, but may be dark along the rim of the hematoma cavity due to ferritin/hemosiderin deposition."}}
{"id": "q_HEMQUIZ_12", "question": "Which of the following statements about ferritin is incorrect?", "golden_answers": [3], "choices": ["It is the principal iron storage molecule found in animal cells.", "It consists of a hollow protein shell into which iron atoms are packed.", "A typical ferritin molecule contains about 2000 iron atoms.", "It is ferromagnetic."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "The ferritin core acts as a solid piece of metal with a single magnetic domain, exhibiting superparamagnetism. Ferromagnetic materials, by contrast, consist of multiple erritinhemosiderin.html domains and retain some residual magnetization after an external magnetic field is removed."}}
{"id": "q_HEMQUIZ_13", "question": "Concerning ferritin and hemosiderin, which statement is true?", "golden_answers": [0], "choices": ["The iron in hemosiderin is insoluble; the iron in ferritin is soluble.", "Both are visible by light microscopy.", "Ferritin is paramagnetic, but hemosiderin is ferromagnetic.", "Both hemosiderin and ferritin have a fixed structure and composition."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "Only (a) is true. Ferritin is much smaller than hemosiderin and can only be visualized at electron microscopy. Both are paramagnetic. Ferritin has a fixed structure and composition; hemosiderin is an amorphous conglomeration of ferritin particles, proteins, and lipids."}}
{"id": "q_HEMQUIZ_14", "question": "Which of the following processes does not affect the appearance of subarachnoid hemorrhage (SAH) as compared to intraparenchymal brain hemorrhage?", "golden_answers": [3], "choices": ["SAH clots are small.", "SAH clots are readily dispersed.", "SAH mixes with cerebrospinal fluid.", "Ambient oxygen levels in the subarachnoid space are low, resulting in faster aging of the hematoma."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "Only (d) is false.  Ambient oxygen levels in the subarachnoid space are high, resulting in slower aging of the hematoma. For example, methemoglobin formation is rare until at least 1 week after ictus."}}
{"id": "q_HEMQUIZ_15", "question": "Concerning CT and MRI of subarachnoid hemorrhage (SAH), which statement is false?", "golden_answers": [1], "choices": ["Acute SAH is better seen on CT than on MRI.", "The best MR sequence for identifying acute SAH is T1-FLAIR.", "Subacute SAH may be better seen on MRI than CT.", "Evidence for remote SAH is much better seen on MRI than CT."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 3.0, "hint": "Option (b) is false. The best sequences for identifying SAH on MRI are T2-FLAIR, GRE/SWI, and DWI."}}
{"id": "q_HEMQUIZ_16", "question": "Which of the following statements concerning the appearance of hemorrhage at very low fields (<0.15 T) is true?", "golden_answers": [2], "choices": ["Intracellular deoxyhemoglobin is noticeably dark on T2-weighted images.", "Intracellular methemoglobin is noticeably dark on T2-weighted images.", "Extracellular methemoglobin is bright on T1-weighted images.", "The center of a hyperacute hematoma is dark on T1-weighted images."], "metadata": {"subject": "MR Contrast Agents and Blood Quiz", "level": 2.0, "hint": "Only (c) is true. Neither intracellular deoxy- and met-Hb are dark on T2 weighted images as they are at high fields. This is because the dephasing is due to susceptibility which scales with the square of the magnetic field. The center of an acute clot is bright on T1-weighted images due to hemoconcentration and protein effect."}}
{"id": "q_GRADSAFE_00", "question": "How many sets of gradient coils does the typical MRI scanner use?", "golden_answers": [2], "choices": ["1", "2", "3", "4"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "The typical MR scanner uses 3 sets of paired gradient coils, one set for each of the x-, y-, and z-directions  Link to Q&A discussion"}}
{"id": "q_GRADSAFE_01", "question": "The magnetic field strength of imaging gradients", "golden_answers": [0], "choices": ["Is much less than that of the main field (Bo)", "Is slightly less than that of the main field (Bo)", "Is the same as that of the main field (Bo)", "Is slightly greater than that of the main field (Bo)"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "The strength of the magnetic fields generated by gradients are less than 3% of the main magnetic field (Bo), so their static effects are of no concern. Rather, it is the time rate of change of these gradient fields (dB/dt) that poses potential safety issues for MR imaging."}}
{"id": "q_GRADSAFE_02", "question": "Which of the following physical effects is not the result of gradient activity?", "golden_answers": [1], "choices": ["Acoustic noise", "Vertigo", "Peripheral nerve stimulation", "Metal implant heating"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Vertigo is primarily an effect due to subject movement in the static magnetic field (Bo). The other choices result from gradients."}}
{"id": "q_GRADSAFE_03", "question": "Concerning acoustic noise due to gradients, which statement is false?", "golden_answers": [1], "choices": ["It is due to vibration of the gradient coils due to rapidly switched electrical currents.", "Acoustic noise in MRI may be temporarily uncomfortable, but it poses no real risk to hearing.", "Echo-planar sequences are especially loud.", "All patients and accompanying family members should be required to use ear protection."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Levels of acoustic noise in an MR scanner may reach 130 dB(A), producing both temporary and permanent threshold shifts (loss of hearing). Children are especially susceptible."}}
{"id": "q_GRADSAFE_04", "question": "Concerning gradient-related electromagnetic fields in patients, which statement is false?", "golden_answers": [3], "choices": ["It is the coexistent electric field, rather than the gradient magnetic field, which causes peripheral nerve stimulation.", "Peak electric field values occur during the ramp up and ramp down periods of the gradients.", "Electric fields in a patient are concentrated superficially and at bone/fat/muscle junctions.", "The strongest gradient effects typically occur at magnet isocenter in the middle of the imaged field-of-view."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Answer d) is false. The centers of the paired gradient coils are located on either side of isocenter, and the strongest gradient effects typically occur toward the ends of the scanner and outside the imaged field-of-view."}}
{"id": "q_GRADSAFE_05", "question": "Concerning the strength-duration curve for nerve depolarization, which one of the following is true?", "golden_answers": [0], "choices": ["The strength-duration curve plots the threshold for electrical stimulation as a function of stimulus strength and duration.", "The shape of the strength-duration curve is approximately linear.", "The rheobase is the minimum time required to stimulate a nerve regardless of stimulus strength.", "The chronaxie is the minimum voltage required to stimulate a nerve at any duration."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Only a) is true. The shape of the strength-duration curve is not linear, but has a hyperbolic/exponential shape. The rheobase represents the minimum stimulus required for excitation, while the chronaxie is the required time for a depolarizing stimulus applied at twice the rheobase value."}}
{"id": "q_GRADSAFE_07", "question": "Which implant would be least likely to demonstrate gradient-induced heating?", "golden_answers": [1], "choices": ["Total hip prosthesis", "Deep brain stimulator electrode", "Cardiac pulse generator", "Implanted infusion pump"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Because gradient switching frequencies are 100,000 times lower than RF frequencies, induced electrical currents are not confined to the \"skin\" of the implant, but circulate throughout it. Gradient-induced heating occurs in implants with large cross sections having low-resistance closed current loops (such as hip prostheses, pulse generators, and infusion pumps). A deep brain stimulator electrode would heat due to the RF antenna effect, not gradient action."}}
{"id": "q_GRADSAFE_08", "question": "Concerning gradient-induced heating, which of the following is incorrect?", "golden_answers": [0], "choices": ["Gradient heating is typically more important the RF heating in causing tissue injury.", "Changing gradients heat the implant itself.", "Gradient heating is more likely with fast, high slew rate sequencies like echo-planar imaging.", "Gradient heating affects bulky implants with large transverse cross-sections."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Gradient heating is much less important than RF heating, and to my knowledge, no serious injuries have been reported from it. Gradient heating involves the implant itself, with secondary heating of the soft tissues, while RF heats the peri-implant tissues directly Link to Q&A discussion"}}
{"id": "q_RFSAFETY_00", "question": "Concerning RF-transmit body coils, which of the following is false?", "golden_answers": [1], "choices": ["They consist of multiple rungs in a so-called “bird cage” configuration.", "In addition to transmission they are commonly used for reception of the RF signal.", "They do not extend the full length of the body coil.", "They cannot be seen by the patient."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "RF body coils are essentially used only for RF transmission, not reception of the MR signal. (Answer b is false). Local receive coils placed near or on the patient are used for this purpose. The other statements are true."}}
{"id": "q_RFSAFETY_02", "question": "Concerning the use of RF-transmit body coils", "golden_answers": [0], "choices": ["They are required for clinical spine imaging", "They are required for clinical head imaging", "They are required for clinical knee imaging", "They are required for phosphorus spectroscopy of the calf muscle"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Only answer a) is true.  For clinical head and knee imaging, as well as phosphorus spectroscopy, local transmit-receive RF-coils may be employed, and if so, the body RF coil is not activated."}}
{"id": "q_RFSAFETY_03", "question": "Radiofrequency fields are part of the electromagnetic spectrum considered to have frequencies lying in the approximate range of", "golden_answers": [3], "choices": ["64 MHz to 128 MHz", "3 kHz to 300 MHz", "3 kHz to 1 GHz", "3 kHz to 300 GHz"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Although many definitions for the frequency limits for RF exist, most extend from the kHz to the hundreds of GHz range, so answer d) is the best choice"}}
{"id": "q_RFSAFETY_04", "question": "Concerning the thermal effects of RF-irradiation as used in MRI, which statement is true?", "golden_answers": [2], "choices": ["T1 relaxation with energy transfer from nuclei to the lattice makes a significant contribution to tissue heating.", "The RF magnetic and electric fields point in opposite directions.", "The coexistent electric field (E), not the magnetic field (B1) per se, is responsible for nearly all the RF-thermal effects in MRI.", "About half of transmitted RF power is absorbed by nuclei."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Only a small fraction of RF power, 2% or less, is absorbed by nuclei, and thus T1 relaxation releasing this energy makes no significant contribution to heating. Time-dependent E and B1 fields always coexist, and it is the electric field that drives tissue currents and produces heating. (Answer c is correct). By the Faraday-Maxwell equation, the E field “curls around” the changing B1 field in a perpendicular fashion."}}
{"id": "q_RFSAFETY_05", "question": "Which mechanism of RF-induced tissue heating is unlike the others?", "golden_answers": [3], "choices": ["Resistive heating", "Joule heating", "Ohmic heating", "Dielectric heating"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "The correct answer, (d) Dielectric heating, is caused by reorientation of polar molecules, especially water, with the rapidly changing RF electric field.  The first three choices (a), (b), and (c) are all synonyms and represent heating caused by the movement of ionic molecules accelerated by changes in the RF electric field."}}
{"id": "q_RFSAFETY_06", "question": "Which mechanism is primarily responsible for making my bowl of soup warm up in the microwave oven?", "golden_answers": [3], "choices": ["Resistive heating", "Joule heating", "Ohmic heating", "Dielectric heating"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "The correct answer again is (d) Dielectric heating.  Microwaves act to realign polar molecules, which collide with others, dispersing their kinetic energy as heat. Joule, Resistive, or Ohmic heating (all are synonyms) produce thermal effects by movement of ions and are more important at frequencies lower than microwaves."}}
{"id": "q_RFSAFETY_07", "question": "The units for specific absorption rate (SAR) are", "golden_answers": [0], "choices": ["Watts per kilogram", "Watts per second", "Joules per kilogram", "Joules per second"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "SAR is power (watts) deposited in a certain mass of tissue (kg). Answer a) is correct."}}
{"id": "q_RFSAFETY_08", "question": "Concerning SAR which of the following is false?", "golden_answers": [1], "choices": ["SAR is proportional to tissue electrical conductivity.", "SAR decreases with increasing body size.", "SAR is proportional to the square of both Bo and B1.", "SAR is proportional to the duty cycle."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Answer b) is false. SAR increases exponentially with increasing body size and is thus a significant concern with large or obese patients."}}
{"id": "q_RFSAFETY_09", "question": "What are the units of measurement for the duty cycle?", "golden_answers": [2], "choices": ["Seconds", "Watts/kg", "Percent", "Joules/second"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Duty cycle is the fraction of time in a pulse sequence that RF is being transmitted, so it is measured in percent (%).  Link to Q&A discussion"}}
{"id": "q_RFSAFETY_10", "question": "A 50-kg woman is imaged using a 3-minute pulse sequence having an SAR of 2.0 W/kg.  The total RF energy absorbed is", "golden_answers": [3], "choices": ["180 Joules", "300 Joules", "3000 Joules", "18,000 Joules"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "To solve this you have to convert minutes to seconds and recognize that 1 Watt = 1 Joule per second. Total energy = mass x time x SAR = (50 kg) x (180 s) x 2 (W/kg) = 18,000 J."}}
{"id": "q_RFSAFETY_11", "question": "Consider two otherwise identical gradient echo pulse sequences, the first using an RF-flip angle (α) = 15º and the second using α = 30º.  The SAR of the second pulse sequence is", "golden_answers": [2], "choices": ["Twice as large as the first.", "Half as large as the first.", "Four times as large as the first.", "One fourth as large as the first."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "For uniform rectangular RF pulses, the SAR is approximately proportional to the square of the RF-flip angle (α), so doubling the flip angle quadruples the SAR."}}
{"id": "q_RFSAFETY_12", "question": "Which of the following is not the name of an MRI Operating Mode based on perceived risk to subjects as defined by the International Electrotechnical Commission (IEC)?", "golden_answers": [3], "choices": ["Normal", "First Level", "Second Level", "Third Level"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "There is no Third Level Operating Mode. Also note that Normal is the lowest level and is not the same as First Level."}}
{"id": "q_RFSAFETY_13", "question": "Concerning Operating Modes for MRI as defined by the International Electrotechnical Commission (IEC) which statement is false ?", "golden_answers": [0], "choices": ["The same SAR limits apply regardless of whether a volume transmit or local transmit coil is used.", "Higher SAR limits are allowed for extremity imaging than trunk imaging.", "Other factors (such as static field strength and rates of time-varying gradients) are used in addition to SAR levels when defining the MRI Operating Mode", "Second level operation can only be performed under an appropriate ethics/human studies/institutional review board protocol"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Different limits apply depending on the type of transmit coil (volume vs local) as well as area imaged, so a) is false.  The other statements are true."}}
{"id": "q_RFSAFETY_14", "question": "When is it acceptable to change from Normal to First Level Controlled Operating Mode?", "golden_answers": [2], "choices": ["Whenever one needs to increase the number of slices for a given TR.", "Whenever one needs to perform more rapid imaging in a moving patient.", "Whenever deemed necessary and under supervision of a physician.", "Whenever the patient’s body weight is unknown and may be underestimated."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Answer c) is correct. First Level Controlled Operating Mode requires physician supervision and explicit recognition by the MR tech or operator to confirm awareness of potential risks. The other choices are possible reasons one might wish to upgrade the operating mode, but cannot be done without physician assessment and supervision."}}
{"id": "q_RFSAFETY_15", "question": "Which one of the following pulse sequences would have the lowest SAR?", "golden_answers": [0], "choices": ["A single-shot echo-planar diffusion scan of the bran", "A T2-weighted turbo spin-echo scan of the pelvis", "A T1-weighted, fat suppressed spin-echo image of the cervical spine", "A 2D time-of-flight MRA of the lower extremities"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "The EPI diffusion scan, using predominantly recalled echoes by gradient reversal, would have the lowest SAR of the scans listed."}}
{"id": "q_RFSAFETY_16", "question": "Which of the following technical parameter changes alone would not be useful in reducing SAR?", "golden_answers": [1], "choices": ["Increase TR", "Increase number of slices", "Reduce flip angle", "Use of hyperechoes"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Option b), increasing the number of slices for a given TR would actually increase SAR, not decrease it. The other answers are true."}}
{"id": "q_RFSAFETY_18", "question": "All of the following are trade-offs for the use of low SAR RF-pulses except", "golden_answers": [0], "choices": ["More slice cross-talk", "Longer minimum TE values", "Longer imaging time", "Fewer slices for a given TR"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Low SAR pulses are played out at lower amplitude but longer duration than normal RF pulses. This means they operate with lower transmit bandwidths and thus have better slice profiles. So slice cross-talk is reduced, not increased (option a is false). The longer duration low SAR pulses impair minimum TE and TR values, interecho spacing for TSE sequences, and hence may increase imaging time."}}
{"id": "q_RFSAFETY_19", "question": "Which of the following physical mechanisms is not an important factor in RF-induced thermal injury?", "golden_answers": [1], "choices": ["Inductive heating", "Magnetohydrodynamic effect", "Heating of a resonant loop", "Antenna effect"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "The magnetohydrodynamic effect is a current generated by ions in blood moving though a magnetic field. Although it may be responsible for altering the appearance of the EKG, it has no direct harmful physical effects such as thermal injury."}}
{"id": "q_RFSAFETY_20", "question": "Which of the following statements about the “antenna effect” is false?", "golden_answers": [2], "choices": ["It explains SAR hot spots at the end of a wire or electrode.", "It results from standing waves along the length of the wire.", "The effect is maximal when the wire measures close to the RF wavelength.", "Wires measuring about 26 cm at 1.5T and 13 cm at 3.0T are the most likely to experience this phenomenon."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Answer c) is false. The antenna effect is maximal when the length of the wire is one-half of the RF wavelength.  The wavelength actually varies depending on the tissue, but for water-containing tissues the 26 cm and 13 cm values are a reasonable starting point."}}
{"id": "q_RFSAFETY_21", "question": "Which of the following would not be an acceptable position for a patient undergoing MRI?", "golden_answers": [1], "choices": ["Prone", "Hands clasped across lap", "Arms straight up", "Supine with knees bent at 90º"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Skin-to-skin contact must be avoided to prevent induced current loops and possible burns during MRI. So crossing arms or legs and holding hands (answer b) should not be permitted  Link to Q&A discussion"}}
{"id": "q_RFSAFETY_22", "question": "What should be done if an MR patient has a large tattoo?", "golden_answers": [1], "choices": ["Nothing; they are totally safe to scan except in rare cases.", "Warn the patient about heating and to notify tech immediately if any discomfort.", "Allow scanning, but apply an ice pack to the tattoo during the procedure.", "Do not scan the patient; large tattoos are contraindicated due to high risk of burns."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "We recommend strategy in answer b), to warn the patient to be aware of any discomfort and that burns can occasionally occur. Although some centers have recommended applying an ice pack, this seems unproven and unnecessary."}}
{"id": "q_RFSAFETY_23", "question": "Concerning transdermal medication patches, which statement is incorrect?", "golden_answers": [0], "choices": ["All patches must be removed prior to scanning.", "Only metal-backed patches must be removed.", "A metal back patch need not be removed if it is not in the region of the transmit RF-coil.", "Before removing a patch for MRI, the patient’s physician should be contacted to be sure it is safe for the patient to not receive her patch medication for the duration of the scan."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Only metal-backed patches within the RF field need to be removed, so statement a) is false. Those made of cloth or paper pose no danger."}}
{"id": "q_RFSAFETY_24", "question": "Concerning large patients that may touch the walls of the scanner, which of the following is true?", "golden_answers": [2], "choices": ["They may feel uncomfortable and experience claustrophobia, but are in no medical danger.", "Ideally a sheet should be placed between the patient and the wall to avoid bacterial contamination of the scanner from the patient’s skin.", "Special foam padding provided by the manufacturer should be used to prevent the patient from touching the walls.", "It is OK to scan the patient without padding if they are too big."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Both cutaneous and deep burns can occur if the patient touches the inner wall of the MRI scanner. In this location local RF fields are the highest and there can be capacitive coupling with the RF coil (that is just a few cm away). Specialized foam padding should always be used (answer c is correct). Thin sheets or blankets or nothing is not acceptable."}}
{"id": "q_RFSAFETY_25", "question": "Concerning wires and cables within the bore of the MR scanner, which statement is false?", "golden_answers": [1], "choices": ["Skin contact must be avoided by padding or positioning.", "The wires should be run down along the sidewall of the MR bore parallel to the main magnetic field.", "The wires should not be crossed.", "If more than one wire is exiting, it is ideal to leave a little space between them to prevent capacitive coupling."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Option b) is false. Wires should ideally be run down the center of the MR system out between the patient's legs. Wires located close to the walls of the scanner would be close to the RF coil and be at risk for induced currents."}}
{"id": "q_RFSAFETY_26", "question": "Concerning Specific Energy Dose (SED) and Specific Absorption Rate (SAR), which statement is true?", "golden_answers": [1], "choices": ["They are essentially the same, except for a conversion factor to correct for units of measurement.", "The units for SED are Joules/kg.", "Both represent rates of energy absorption by the body during an MRI scan.", "If every sequence in a scanning protocol has SAR values that lie safely within regulatory limits, the SED cannot be excessive."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "SED and SAR are different. SAR is the rate of energy absorption, measured in W/kg. SED is not a rate, but the total energy absorbed by the body during an entire MRI scan, measured in Joules/kg (answer b is true). It is possible, for example, for each sequence in an MRI scanning protocol to lie safely within regulatory SAR limits, yet total energy deposition in the patient over the course of the entire exam to be excessive. Some MR manufacturers now compute and report both SAR and SED, and limit scanning in a full exam if the accumulated SED is too high."}}
{"id": "q_RFSAFETY_27", "question": "A 50-kg woman undergoes an MR protocol that consists of two sequences: Sequence 1, lasting 2 minutes, with SAR = 1 W/kg; followed by Sequence 2, lasting 4 minutes, with SAR = 2 W/kg.  The SED for the entire protocol is calculated to be", "golden_answers": [2], "choices": ["10 J/kg", "100 J/kg", "600 J/kg", "800 J/kg"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Using the defining formula SED = SAR x acquisition time, remembering that minutes must be converted to seconds, and that 1 Watt = 1 Joule/sec, we calculate for Sequence 1: SED1 = (1 W/kg) x (120 s) = 120 J/kg and for Sequence 2: SED2 = (2 W/kg) x (240 s) = 480 J/kg.  So the total SED is 120 + 480 = 600 J/kg (answer c)."}}
{"id": "q_RFSAFETY_28", "question": "All of the following statements about the B1+ field and  B1+rms are true except for", "golden_answers": [0], "choices": ["The B1+ field rotates in the opposite direction to nuclear precession.", "SAR is directly proportional to [B1+rms]²", "SAR is directly proportional to [Bo]², but B1+rms is independent of Bo.", "The strength of the B1+ field scales linearly with the voltage supplied to the transmitter."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "The B1+ field rotates in the same direction as nuclear precession, so option a) is false. B1+ is the component of B1 responsible for tipping of the net magnetization. It can be computed directly by measuring the relative voltage driving the RF-transmitter, and so depends less on the patient or main magnetic field."}}
{"id": "q_RFSAFETY_29", "question": "Concerning occupational exposure to MRI in the clinical environment, which one of the following statements is true?", "golden_answers": [1], "choices": ["Consistent regulatory limits for occupational exposure to magnetic fields exist throughout Europe and the Americas.", "MRI staff working around scanners with fields of 7T or higher commonly experience nausea, dizziness, unsteadiness, and/or see flashes of light.", "There is nothing that can be done to reduce these short-term sensory effects.", "Pregnant MR technologists are at increased risk for miscarriages or premature births."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Short-term sensory changes (including nausea, vertigo, and/or magnetophosphenes) are experienced by about one-fourth of MR staff working around 7T scanners. (Answer b is true.) These effects can be mitigated by moving slowly around the scanner and avoiding the scanner bore entrance. Unfortunately, national and international regulations about EM field exposure are varied and often contradictory.  Pregnant MR technologists and other healthcare workers in the MRI environment do not seem to have increased risk for miscarriages or other birth-related problems."}}
{"id": "q_RFSAFETY_30", "question": "Do cell phones cause cancer?", "golden_answers": [2], "choices": ["Definitely yes", "Definitely no", "Probably no, but some data suggests a potential small effect.", "Probably yes, but some data suggests no effect."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Cell phone use has been claimed to be associated with gliomas, meningiomas, and vestibular schwannomas.  Much of the literature in support of these claims is clearly flawed, and at least two large studies have found no statistically significant effects. There are, however, a few studies suggesting a small effect, perhaps most strongly for vestibular schwannomas and meningiomas. My answer is therefore c), though you might have your own opinions on this one."}}
{"id": "q_SAFEDEV_00", "question": "Why did early regulators establish the 5-gauss line as a safety limit for exposure of the general public around MRI facilities?", "golden_answers": [2], "choices": ["It is the field strength where a ferromagnetic cerebral aneurysm clip begins to move.", "It is the field strength where a paper clip or other equivalent small metal object will fly into the scanner.", "It is the field strength where 1970’s era pacemakers might begin to malfunction.", "It is approximately 10 times the earth’s magnetic field."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Different origin stories exist for the 5-guass line, but there is general agreement that it was based on the field strength at which certain 1970’s era pacemakers began to malfunction. The observed malfunction was likely due to closure of the internal reed switch, a magnetically sensitive component which changes the operating mode of the pacemaker. The 5-gauss limit as a safety line was officially recommended by the FDA in 1983."}}
{"id": "q_SAFEDEV_01", "question": "Concerning the safety of cerebral aneurysm clips in the MR environment, which statement is incorrect?", "golden_answers": [0], "choices": ["If an aneurysm clip is safe by testing at 3.0T, it will be safe at 7.0T.", "Ferromagnetic aneurysm clips have not been manufactured since the mid-1980’s.", "A patient with a commercially produced aneurysm clip implanted within the last 20 years is safe to scan at 3.0T.", "Always review the operative note or patient’s implant card prior to scanning to ensure MR safety, especially in the 7.0T environment."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Notwithstanding the great reticence of scanning patients with aneurysm clips, the risk in the modern era is miniscule, as ferromagnetic clips have not been produced since the 1980’s. All modern aneurysm clips are composed of titanium titanium-alloys, MP35N (nickel/chromium/cobalt), Elgiloy/Phynox (cobalt/nickel/iron) or other non- or at most minimally ferromagnetic properties. Thus virtually any cerebral aneurysm clip implanted in the last 25 years will be MR compatible at least up to 3.0T. However, a few clips that are safe at 3.0T, especially those made of Elgiloy or stainless steel, have exhibited very strong torques at ultra high fields, so it cannot be assumed that safety at 3.0T implies safety at 7.0T."}}
{"id": "q_SAFEDEV_02", "question": "A patient with a recently placed programmable shunt placed is referred for head MRI. What do you do?", "golden_answers": [2], "choices": ["Do not scan the patient. A programmable shunt is an absolute contraindication to MRI.", "Confirming that the shunt is MR Conditional at up to 3.0T, scan the patient and send him home.", "Send the patient to neurosurgery clinic immediately after the scan to have his valve pressure checked.", "Tell the patient to make an appointment with his neurosurgeon within the next week to have his valve pressure checked."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "All currently manufactured programmable shunt systems are considered MR Conditional up to 3.0T. The main risk of MRI is unintentional resetting of the valve pressure. This occurs in up to 40% of patients with Codman-Hakim® valves and even up to 10% of valves marketed as \"MR immune\". Within 4 hours after exposure to MRI, all patients must have their shunt pressures interrogated and potentially reprogrammed to the original settings."}}
{"id": "q_SAFEDEV_03", "question": "Concerning precautions that need to be followed for MR conditional intracranial pressure monitoring systems, which statement is false?", "golden_answers": [3], "choices": ["Obey the usual restrictions on field strength, spatial gradient field, slew rate, and SAR.", "Verify the sensor is working properly prior to MRI.", "Disconnect all removable cables and wires from the device.", "Make sure non-removable wires are arranged in a straight line along the bore of the scanner and away from the patient’s head."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Statement d) is false. To prevent excessive RF-heating of the sensor tip, the non-removable wires and wire-containing tubing must not lie in a straight-line but be specially positioned in a coil-like configuration of several small loops on or near the patient's head. Sophysa even provides a special holder to wrap and secure the wires of their ICP sensor."}}
{"id": "q_SAFEDEV_04", "question": "Which one of the following is the most significant safety concern with the scanning of a patient with a deep brain stimulation system?", "golden_answers": [1], "choices": ["Permanent damage to the implanted pulse generator", "Thermal burn at the electrode tip", "Cutaneous burns along ascending wires in the neck", "Induction of seizures"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "The primary MR safety concern for DBS systems is heating at the electrode tip due to induced currents and the antenna effect. Antennas capture electromagnetic waves and develop standing-wave patterns of voltage and current that are concentrated near their tips. Three clinical cases have been reported in association with MRI, including one leaving permanent neurologic deficits."}}
{"id": "q_SAFEDEV_05", "question": "Why is it recommended that eye makeup be removed prior to MRI?", "golden_answers": [1], "choices": ["This is a myth; eye makeup doesn’t have to be removed.", "It can cause significant image artifacts around the orbit.", "Severe burns can occur on the eyelids.", "Corneal injury and blindness can occur."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "All eye make-up, especially mascara, should be removed prior to imaging.  Such cosmetics often contain iron oxides that create a local artifact and may even result in eye irritation during MR imaging. No serious injuries have been reported."}}
{"id": "q_SAFEDEV_06", "question": "Which of the following orbital implants should elicit the most concern from an MR safety perspective?", "golden_answers": [3], "choices": ["Artificial intraocular lenses", "Contact lenses", "Scleral band", "Retinal tacks"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Although uncommonly used today, some retinal tacks (used for repair of complex detachments) are considered MR unsafe or MR conditional. The other items on the list should present no safety concerns."}}
{"id": "q_SAFEDEV_07", "question": "What is the major safety concern for MR imaging of cochlear implants?", "golden_answers": [0], "choices": ["Movement/dislodgement of the internal magnet", "RF-induced heating at the tip of the cochlear electrode due to the “antenna effect”", "Electronic shorting/malfunction of the electronic stimulator", "Scalp burns adjacent to the subcutaneous receiver coil"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Pain from magnet movement occurs in a substantial fraction of patients. It may be minimized by wrapping the head with a tight-fitting elastic bandage prior to entering the scanner. In some cases the internal magnet must be removed and replaced as a condition of scanning. In some cases the magnet may be completely dislodged from its base. The antenna effect is not a concern due to the short length of the wire/electrode."}}
{"id": "q_SAFEDEV_08", "question": "Which of the following dental implants would pose the biggest safety concern in MRI?", "golden_answers": [3], "choices": ["Metal crowns and bridges", "Amalgam fillings", "Braces", "Magnetic dentures"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Conventional (all porcelain/acryllic dentures) are of no concern, but magnetic dentures contain permanent magnets embedded in their periphery that will be attracted to the main magnetic field.  These should be removed prior to scanning. Metal crowns, bridges, and especially braces will create substantial artifacts, but only rare reports of problems during MRI have been reported."}}
{"id": "q_SAFEDEV_09", "question": "Which upper airway device should be viewed as a potential safety concern in the MR environment?", "golden_answers": [2], "choices": ["Non-cuffed endotracheal tube", "Endotracheal tube with spring-loaded pilot balloon valve", "Reinforced endotracheal tube", "Laryngeal mask airway"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "The only upper airway devices of potential concern would be reinforced endotracheal tubes that contain a metal coil (usually stainless steel) spirally wound in the wall of the tube to prevent kinking. Many are considered to be MR Unsafe."}}
{"id": "q_SAFEDEV_10", "question": "What is the major MR safety concern about breast tissue expanders?", "golden_answers": [1], "choices": ["Loss of saline due to magnetic effects on the valve mechanism", "Dislodgment of the MAGNA-SITE®  port", "Cutaneous burns over the port", "Melting of the silicone capsule adjacent to the port"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Most breast tissue expanders use a MAGNA-SITE®  port for injection. This contains a central permanent magnet for localization purposes that may become dislodged in the MR field. Pain and localized heating have been reported, but no burns. Most manufacturers have declared their tissue expander systems to be MR Unsafe."}}
{"id": "q_SAFEDEV_11", "question": "What should be done if a patient with an inferior vena cava (IVC) filter needs a scan?", "golden_answers": [3], "choices": ["He’s out of luck; nearly all of these are MR Unsafe.", "The patient can be scanned, but no sooner than 6 weeks after implantation.", "The patient can be scanned but should be warned there is a high risk that the filter may migrate.", "The patient can be safely scanned provided MR Conditions are followed."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "All currently manufactured IVC filters are considered MR Conditional at 1.5T and 3.0T. The spontaneous migration rate for properly implanted IVC filters is on the order of 1%, and there is no evidence MRI affects this rate. There is no good reason to wait 6 weeks before MRI."}}
{"id": "q_SAFEDEV_12", "question": "During the last decade in the United States, the leading cause of MRI-related deaths has been", "golden_answers": [0], "choices": ["Infusion pump malfunction", "Projectiles", "Pacemaker malfunction", "Burns"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Surprisingly to many, the answer is infusion pump malfunction. At least a half-dozen such cases were reported in the USA alone, a situation so significant that the Food and Drug Administration (FDA) issued a special safety communication in 2017 to address this issue."}}
{"id": "q_SAFEDEV_13", "question": "Life-threatening effects of the magnetic field on implanted infusion pumps include all except", "golden_answers": [0], "choices": ["Deep peri-implant burns due to RF- and/or Gradient-induced eddy currents", "Increased or decreased rate of drug delivery", "Cessation of pump operation while scanning with delayed restart", "Permanent device failure due to demagnetization of the pump magnet"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Although some heating around infusion pumps, like other metal implants, may occur, severe burns have not been reported and this is not a major concern. The other items (b) – (d) do constitute significant risks for the device."}}
{"id": "q_SAFEDEV_14", "question": "Which of the following intravascular devices should be considered MR Unsafe?", "golden_answers": [2], "choices": ["Aortic stent graft", "Drug-eluting coronary stent", "Swan-Ganz thermodilution catheter", "Vascular closure device"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "In a famous index case from 1988, a portion of a Swan-Ganz catheter outside the patient \"melted\" during MRI.  Since then, Swan-Ganz catheters have been considered MR Unsafe.  Link to Q&A discussion"}}
{"id": "q_SAFEDEV_15", "question": "Failure of drug delivery by an implanted infusion pump affected by a magnetic field is particularly dangerous for which drug?", "golden_answers": [2], "choices": ["Bupivacaine", "Morphine", "Baclofen", "Floxuridine (5-FUdR)"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Intrathecal baclofen via constant infusion is used to treat pain and spasticity. If the infusion is suddenly stopped, a life-threatening baclofen withdrawal reaction may occur.  Temporary disruption of administration of the other drugs would not likely be dangerous."}}
{"id": "q_SAFEDEV_16", "question": "Concerning the following bariatric devices, which should raise the greatest MR safety concerns?", "golden_answers": [2], "choices": ["Adjustable gastric bands", "Gastric balloons", "Gastric electrical stimulators", "External gastric drainage devices"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Gastric electrical stimulators (GES), sometimes called “gastric pacemakers” consist of a subcutaneously implanted pulse generator with leads that attach to the stomach musculature or distal vagal nerves. All currently produced GES devices are considered MR Unsafe. The other bariatric items are made predominantly of plastic and silicone and are either MR Safe or (minimally) MR Conditional."}}
{"id": "q_SAFEDEV_17", "question": "Which of the following contraceptive devices is considered MR Unsafe?", "golden_answers": [1], "choices": ["Copper 7 IUD", "Chinese stainless steel ring IUD", "Filshie tubal ligation clips", "Essure® tubal occlusion devices"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "All the devices listed above are considered MR Conditional except for the Chinese stainless steel ring IUD that is MR Unsafe.  These were distributed exclusively in China between 1988 and 2000. But because millions of such IUDs were implanted, a reasonable possibility exists that a middle-aged or older Chinese woman might still have one in place."}}
{"id": "q_SAFEDEV_18", "question": "Which metal is not commonly used for modern orthopedic implants?", "golden_answers": [0], "choices": ["410 stainless steel", "316L stainless steel", "Cobalt-chromium alloy", "Pure commercial titanium"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "All of the listed metals are used in orthopedic implants except for the 400 series of stainless steels which are ferromagnetic."}}
{"id": "q_SAFEDEV_19", "question": "Why might a surgical supply manufacturer choose to make halos and external fixation rods out of carbon fiber reinforced polymer?", "golden_answers": [2], "choices": ["They are lighter than their metal equivalents.", "They are stronger and more flexible than their metal equivalents.", "They are only weakly conductive.", "They are only weakly ferromagnetic."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "The primary reason for using these materials is that they are essentially non-conductive. When rods or halo ring and pins are made out of conductive metals such as MR-compatible titanium or other non-ferromagnetic alloys, they may result in thermal burns along pin tracts or where the frame is in contact with the skin. Because external fixation devices lie predominantly outside the body (where the E-field is strongest), conductive currents may be induced in the rods."}}
{"id": "q_SAFEDEV_20", "question": "A patient with an external fixation frame complains of tingling and discomfort due to vibration of the frame during scanning.  What is the likely cause of this?", "golden_answers": [1], "choices": ["Resonant amplification of normal scanner mechanical vibrations", "Vibration of the frame due to gradient-induced eddy currents.", "Vibration of the frame due to RF-induced eddy currents.", "Subconscious to-and-fro movement of the frame by the patient due to peripheral nerve stimulation"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Even with fully MR-compatible external fixation arrays, an occasional patient may experience tingling or tugging during scanning, necessitating early termination of the scan. In some instances this is due to vibrations in the frame due to gradient-switching-induced eddy currents. While harmless, these vibrations may be misinterpreted by the patient as heating. The phenomenon is more likely to occur when the fixation device is located far from magnet isocenter."}}
{"id": "q_SAFEDEV_21", "question": "The abbreviation CIED stands for", "golden_answers": [0], "choices": ["Cardiac Implanted Electronic Device", "Cardiac Implanted Electrical Defibrillator", "Cardioverting Internal/External Defibrillator", "Cardiac Internal Excitation Device"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "CIED is a commonly used abbreviation in the medical literature to refer to any Cardiac Implanted Electronic Device used to detect and/or treat rhythm distuburbance. CIED’s include both Permanent Pacemakers (PPMs) and Implanted Cardioverter-Defibrillators (ICDs)."}}
{"id": "q_SAFEDEV_22", "question": "Two-lead CIEDs typically terminate in", "golden_answers": [0], "choices": ["The right atrium and right ventricle", "The right atrium and left ventricle", "The right ventricle and left ventricle", "The left atrium and left ventricle"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Most two-lead CIEDs terminate in the right atrium and right ventricle, allowing for dual-chamber sensing and pacing that follows the nature contraction of the heart  Link to Q&A discussion"}}
{"id": "q_SAFEDEV_23", "question": "Concerning Implanted Cardioverter-Defibrillators (ICDs), which statement is false?", "golden_answers": [1], "choices": ["ICDs are the preferred CIED for treating ventricular fibrillation.", "ICD’s are the preferred CIED for treating symptomatic bradycardia.", "ICD’s are designed to deliver high-energy shocks.", "Some ICDs do not have shock leads in the heart."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "ICD’s are designed to treat tachyarrhythmias like ventricular fibrillation, while permanent pacemakers are preferred for treating symptomatic bradyarrhythmias. Subcutaneous ICDs have their shock leads outside the heart."}}
{"id": "q_SAFEDEV_24", "question": "“Leadless” pacemakers are generally placed in the", "golden_answers": [3], "choices": ["Left atrium", "Left ventricle", "Right atrium", "Right ventricle"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Most leadless pacemakers like the Nanostim™ and Micra™ are placed in the right ventricle. Internal accelerometers allow them to partially sync with right atrial contraction, but essentially they only sense and pace the RV. Because of their small size, they are unable to deliver high-energy shocks for tachyarrythmias."}}
{"id": "q_SAFEDEV_25", "question": "Which of the following pacemaker scenarios would invoke the greatest MR safety concern?", "golden_answers": [1], "choices": ["Scanning a patient with retained epicardial leads", "Scanning a patient with a temporary transvenous pacemaker", "Scanning a patient within 6 weeks of placement", "Scanning a patient with a legacy/non-conditional pacemaker"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Due to the risk of significant lead heating demonstrated in animal models, scanning a patient with a temporary transvenous pacemaker is considered unsafe.  Scanning a patient with a legacy pacemaker carries a small risk (which can be mitigated by using procedures documented by the Heart Rhythm Society (2017)."}}
{"id": "q_SAFEDEV_26", "question": "What is the principal risk associated with scanning a patient with a subcutaneously implanted loop recorder?", "golden_answers": [3], "choices": ["Skin burns over the device", "Permanent malfunction of the device", "Electric, shock-like sensations", "Erasure of previously recorded data"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Loop recorders are considered MR Conditional at 1.5T and/or 3.0T. Because data may be corrupted or erased by magnetic fields, it is recommended that any desired recorded information be downloaded before the MRI and cleared after the MRI."}}
{"id": "q_SAFEDEV_27", "question": "Concerning the MR safety of cardiac valves and annuloplasty devices, which statement is true?", "golden_answers": [1], "choices": ["Most older metal valves are considered MR Unsafe.", "All valves and annuloplasty devices are considered MR Safe or Conditional up to 3.0 T.", "A mandatory 6 week waiting period is required before scanning for all valves.", "A mandatory 6 week waiting period is required before scanning for any valve or annuloplasty device containing metal."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "The results of numerous investigations have demonstrated that metal-containing valves do undergo magnetically induced torques, but the magnitude of this effect is much less than the force exerted by the beating heart itself. This is in part because the metals used in modern mechanical valves (titanium, Elgiloy®) are not ferromagnetic. Even very old stainless steel valves are likewise considered of no danger in MRI. Thus at present, most centers consider all implanted heart valves and annuloplasty rings conditionally safe for MR imaging up to 3.0T, and do not require any waiting period after surgery before they can be scanned."}}
{"id": "q_SSOV_00", "question": "A person with altered mental status is sent from the emergency room for an urgent MRI, but no family, prior scans, or medical history are available. What should you do to ensure reasonable safety for the exam?", "golden_answers": [2], "choices": ["Call the ER physician and ask if there are any reasonable alternatives to MRI in light of the absent history, and if not, go ahead and perform the scan as ordered.", "Use a hand-held ferromagnetic metal detector to exclude a dangerous implant or foreign body", "Obtain x-rays of the head & neck, chest, and abdomen/pelvis as a screening procedure", "Refuse to do the MRI until a full medical history can be obtained."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "In the total absence of medical history, minimum screening prior to MRI should involve x-rays of the head & neck, chest, and abdomen/pelvis which will identify the overwhelming majority of potentially dangerous implants and foreign bodies. So c) is true. Although it is reasonable to ask the ER physician if an alternative imaging exam could be performed instead, it is not sufficient just to carry out the order for the MRI without further safety checks, so a) is false. A hand-held metal detector will not necessarily identify objects deep within the body or those composed of non-ferromagnetic metals, so b) is false. Refusal to do the exam may deny the patient an important and urgent diagnosis that could compromise his health, so d) is also false."}}
{"id": "q_SSOV_01", "question": "Which of the following is considered an “active” implant?", "golden_answers": [0], "choices": ["Implanted infusion pump", "Magnetic dentures", "Cerebrospinal fluid shunt with a programmable valve", "Swan-Ganz catheter"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Active implants contain their own power source, so a), an implanted infusion pump is the only correct answer since it has a battery.  Magnetic dentures and programmable CSF valves contain permanent magnets, but do not have an intrinsic power source. Swan-Ganz catheters may contain wires and electronic sensors, but are powered externally and hence considered “passive” devices."}}
{"id": "q_SSOV_02", "question": "Which of the following is not currently acceptable terminology for the safety of a device in MRI?", "golden_answers": [2], "choices": ["MR Unsafe", "MR Conditional", "MR Compatible", "MR Safe"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Although used before 2005, MR Compatible (c) is no longer acceptable terminology according to ASTM Standard F2503-20.  Many devices manufactured and tested before 2005 may still carry the old labeling, however."}}
{"id": "q_SSOV_03", "question": "Concerning safety labeling of devices, which of the following statements is true?", "golden_answers": [0], "choices": ["A large silicone implant cannot be rated as MR Safe if it contains a single tiny non-ferromagnetic clip deep inside it.", "An MR Conditional device is safe to scan provided the majority of specified conditions are followed.", "Any implant containing a permanent magnet is MR Unsafe.", "If an implant does not undergo movement or heating under rigorous ASTM testing, it can be rated MR Safe."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "To be considered MR Safe, a device must contain no metal components whatsoever. The tiny screw in the silicone implant renders it MR Conditional, so a) is true.  MR Conditional devices must meet all of the conditions specified, so b) is false. Having a permanent magnet inside does not necessarily render a device MR Unsafe (though it may be). Finally, if an implant contains a small amount of metal, even if it does move or heat up under laboratory testing, it cannot be considered MR Safe, only MR Conditional. Hence d) is also false."}}
{"id": "q_SSOV_04", "question": "Concerning projectile incidents in MRI, which of the following is true?", "golden_answers": [1], "choices": ["Worldwide at least a dozen people have died from projectile accidents since the beginnings of MRI.", "All reported deaths have involved ferromagnetic oxygen cylinders.", "Most reported projectile incidents involve small objects.", "An object made of non-ferromagnetic materials can still become a dangerous projectile."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Only two documented deaths have been reported from projectile injuries in MRI – a child in New York in 2001 and a man in Mumbai in 2018. Both were hit with ferromagnetic oxygen cylinders. So a) is false and b) is true. Most reported projectile incidents involve large objects (e.g. wheelchairs, carts, IV poles) inadvertently brought into the MR room, so c) is false. Objects made entirely of non-ferromagnetic materials would be only weakly attracted to the magnetic field and would not pose a danger, hence d) is false."}}
{"id": "q_SSOV_05", "question": "Which of the following statements about metal detectors in the MR setting is false?", "golden_answers": [0], "choices": ["Metal detectors in MRI are very similar to those used for airport screening.", "The Joint Commission now requires all new and renovated MR suites to be equipped with ferromagnetic metal detectors.", "MR metal detectors cannot reliably detect deeply implanted ferromagnetic materials.", "Alarm fatigue can be a problem at sites using MR metal detectors."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Answer a) is false, while the other statements are true.  Airport detectors are designed to the presence of any metal, whereas MRI detectors are designed to alarm in the presence of ferromagnetic metal only. Link to Q&A discussion"}}
{"id": "q_SSOV_06", "question": "Concerning MR imaging in the pregnant patient, which statement is false?", "golden_answers": [0], "choices": ["Because of unknown risks to the fetus, MR should only be performed when the life of the mother or fetus is immediately threatened.", "The administration of gadolinium contrast should be avoided if at all possible.", "Low-SAR sequences are preferred to avoid heating fetal tissue.", "Quiet gradient sequences are preferred to avoid fetal exposure to loud noise after the first trimester."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Although the risk of MR to the developing fetus is extremely low, it may not be zero and thus judicious use of MRI is recommended only after discussion with the patient. Most valid indications for MRI are serious but not immediately life-threating (e.g. maternal stroke, fetal anomaly), so choice a) is false. The other choices are true."}}
{"id": "q_SSOV_07", "question": "Which of the following commonly encountered postoperative items should be further scrutinized as a potential MR safety hazard:", "golden_answers": [2], "choices": ["Skin staples", "IV catheter and tubing", "EKG pads", "Penrose drain"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "EKG pads, answer c) should draw the most concern, as those not certified for MRI contain metal and may cause skin burns. Skin staples are made of non-ferromagnetic metal and pose no risk of injury or dislodgment. IV catheters and tubing are safe (provided no metal clamps are attached). Finally, penrose drains contain no metal and are also MR Safe."}}
{"id": "q_SSOV_08", "question": "For which patients is temperature monitoring during MRI not required?", "golden_answers": [0], "choices": ["Healthy teenagers", "Healthy infants", "Anesthetized patients", "Elderly patients"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 1.0, "hint": "Otherwise healthy teenagers and non-elderly adults undergoing routine MRI would be unlikely to experience thermodynamic instability, and not require temperature monitoring. So answer a) is correct. The other listed types of patients are at risk and should be monitored."}}
{"id": "q_SSOV_09", "question": "The most reliable device to measure body temperature during MRI is", "golden_answers": [1], "choices": ["A rectal fiberoptic probe", "An esophageal fiberoptic probe", "A foley catheter thermistor", "An LCD skin detector placed in the axilla"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "The best answer is b), a probe with either a fluorotopic or gallium-arsinide (GaAs) detector and fiberoptic cable placed in the distal third of the esophagus."}}
{"id": "q_SSOV_10", "question": "In which of the following orbital locations would the presence of small piece of metal not be a contraindication to MRI?", "golden_answers": [2], "choices": ["Floating in the vitreous humor", "In the retroconal space", "In the lacrimal gland", "On the conjunctiva"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "The lacrimal gland, answer c) is sufficiently far away from vital visual structures to cause injury if magnetically induced displacement occurred."}}
{"id": "q_SSOV_11", "question": "Considering the use of orbital CT to screen for metallic foreign bodies prior to MRI, which of the following is false?", "golden_answers": [0], "choices": ["Orbital CT should be performed routinely on all machinists, pipe fitters, foundry workers, or anyone with similar occupational exposure to metal fragments.", "Plain films of the orbits are an acceptable alternative to CT.", "Low-dose CT techniques should be employed.", "CT may detect metal fragments too small to be of clinical concern for MRI."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Simply possible exposure to metal by virtue of their work is, in my opinion, not enough to warrant expensive screening by CT if there is no known history of injury. The actual risk of significant eye injury is exceedingly rare, with less than a half dozen cases reported over 40 years. So answer a) is false. The other statements are all true."}}
{"id": "q_SSOV_12", "question": "Concerning bullets and ballistic fragments, which statement is true?", "golden_answers": [3], "choices": ["A hand-held ferromagnetic metal detector can reliably determine whether a bullet is made of lead or steel.", "Dual energy CT can reliably determine whether a bullet is made of lead or steel.", "For the last 25 years in the USA, steel-jacketed rifle bullets have been illegal to sell or possess.", "Deformity of a bullet fragment or a debris trail seen on x-ray suggests the projectile is not made of steel."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Only answer d) is correct, but such findings are not definitive, just strongly suggestive about composition.  The other choices are all false. If the bullet sets off the alarm on a hand-held detector it is ferromagnetic, but a negative result is inconclusive. Likewise, although dual-energy CT and other techniques hold promise, technical issues still exist. Finally, steel-jacketed bullets are illegal in the US for handguns, but not for rifles."}}
{"id": "q_SSOV_13", "question": "In assessing a patient with a presumed ferromagnetic bullet or shrapnel, which factor is the most important in assessing risk of performing an MRI?", "golden_answers": [0], "choices": ["Location of the fragment", "Shape of the fragment", "Length of time since implantation", "Whether it was acquired in a military setting"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Like real estate, it’s all about location, location, location. Choice a) is the best choice. If the foreign body is embedded in soft tissue like the brain, even with scarring it can still move appreciably when placed in a magnetic field and cause appreciable local tissue damage. Conversely, fragments embedded in firm tissue like muscle, bone, or tendon, are less likely to move. The shape is important, as long jagged pieces are more dangerous than small round ones. And the longer it has been since injury, the more time has passed for development of scarring/fibrosis that would restrict movement in a magnetic field.  But location trumps shape and time in relative importance. Having been acquired in a military setting increases the probability that the fragment is ferromagnetic, but the question states you have already presumed this composition."}}
{"id": "q_STATIC_00", "question": "Which of the following statements about ferromagnetism is false?", "golden_answers": [0], "choices": ["By definition all ferromagnetic materials must contain at least some iron.", "Ferromagnetism results when electron spins in magnetic domains align.", "As a ferromagnetic substance becomes magnetized, the magnetic domains change in size and shape.", "Hard ferromagnetic materials retain appreciable magnetization when removed from an external magnetic field."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Notwithstanding the name, ferromagnetic materials do not need to contain iron; they only need to form magnetic domains with the capacity to become magnetized. Nickel, cobalt, chromium, manganese, and several rare earth elements and their alloys are ferromagnetic. Hence a) is false. Statements b), c), and d) are true."}}
{"id": "q_STATIC_01", "question": "Which of the following metals is not considered ferromagnetic?", "golden_answers": [3], "choices": ["Nickel", "Cobalt", "Chromium", "Magnesium"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Manganese, but not magnesium (d), is ferromagnetic."}}
{"id": "q_STATIC_02", "question": "Concerning stainless steels, which of the following is false?", "golden_answers": [1], "choices": ["400 series stainless steels are ferromagnetic, while 300 series are non-magnetic.", "Austenitic stainless steels are ferromagnetic, while martensitic stainless steels are non-magnetic.", "Since 1990 the FDA has required all steel implants to be made of non-ferromagnetic stainless steel.", "Even non-ferromagnetic stainless steel can develop ferromagnetic properties if bent or stretched during machine working."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Answer a) is true but b) is false because the names have been reversed: martensitic (= 400 series) steels are ferromagnetic, while austenitic (= 300 series) steels are non-magnetic. Both c) and d) are true."}}
{"id": "q_STATIC_03", "question": "Concerning magnetic saturation, which statement is false?", "golden_answers": [3], "choices": ["Nearly all iron alloys saturate in the range of 1-2 Tesla.", "All ferromagnetic materials become saturated in a 3.0T field.", "It is impossible to create a permanent iron magnet having a field greater than 2.5 Tesla.", "The maximum strength of a permanent magnet is independent of its saturation point."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Option d) is false. The saturation point limits the maximum attainable strength of a permanent magnet or iron core electromagnet, which in most cases is well below 2 Tesla. Answers a)-c) are true  Link to Q&A discussion"}}
{"id": "q_STATIC_04", "question": "An implant made of which of the following materials could pose a safety risk because of ferromagnetic properties:", "golden_answers": [2], "choices": ["Platinum", "Nitinol (Ni-Titanium alloy)", "Silicon steel", "Gold"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Answer c), silicon steel, is highly ferromagnetic and unsuitable as an implant material. The others are essentially non-magnetic (platinum and Nitinol mildly paramagnetic, gold mildly diamagnetic)"}}
{"id": "q_STATIC_05", "question": "Which of the following rare earth elements is commonly used to make room temperature permanent magnets?", "golden_answers": [0], "choices": ["Neodymium", "Magnetodynium", "Holmium", "Dysprosium"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Neodymium (a) doped with iron and boron is commonly used as a base for room temperature permanent magnets, as is samarium-cobalt. Holmium and dysprosium are highly ferromagnetic below 20 ºK but lose this property at higher temperatures.  Choice b), magnetodynium, is not an element!"}}
{"id": "q_STATIC_06", "question": "Which metal or alloy in the list below would be expected to produce the largest susceptibility artifact on gradient-echo imaging?", "golden_answers": [3], "choices": ["Lead", "Copper", "Aluminum", "Nitinol (Ni-Ti alloy)"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Nitinol, answer d) has the largest magnetic susceptibility due to its nickel content and would produce the largest artifact."}}
{"id": "q_STATIC_07", "question": "Concerning the hysteresis curve for a ferromagnetic material, which of the following is true?", "golden_answers": [0], "choices": ["The curves for a material changes after its first time exposure to an external field.", "Coercivity is the magnetization that remains once the external field has been removed", "Reversing the direction of the magnetic field cannot reverse the magnetization.", "The hysteresis curves for a hard ferromagnetic material have small coercivities."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Only a) is true. A “virgin” material (i.e. one never exposed to a large external field) begins with zero or minimal internal magnetization, that grows to a maximum (the saturation value) as the external field is applied. When this field is removed, the magnetization generally does not return to zero but remains at a positive value - the remanence -  not “coercivity” as falsely stated in b).  Reversing the external field can reverse the magnetization as long as it has magnitude greater than the coercivity value (answer c is false). Hard ferromagnetic materials are difficult to demagnetize, with very wide hysteresis curves and hence large coercivities (answer d is false)."}}
{"id": "q_STATIC_08", "question": "Concerning demagnetizing fields, which statement is false?", "golden_answers": [3], "choices": ["The demagnetizing fields for diamagnetic and paramagnetic materials are so small that they may effectively be disregarded.", "The demagnetizing field (D) points in the opposite direction to the magnetization (M)", "The demagnetizing field (D) points in the opposite direction to the external field (Bo)", "The demagnetizing field (D) increases the net magnetic field inside an object."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 4.0, "hint": "Answer d is false. The demagnetizing field, by opposing M and B, decreases the net magnetic field inside an object."}}
{"id": "q_STATIC_09", "question": "Concerning the effects of demagnetizing fields, which statement is false?", "golden_answers": [0], "choices": ["Demagnetizing fields increase the apparent magnetic susceptibility of weakly ferromagnetic objects.", "The apparent susceptibility of an object made of a strongly ferromagnetic material primarily depends on its shape, not its specific composition.", "Demagnetizing fields in ferromagnetic materials reduce the size of the external field needed to achieve magnetic saturation.", "Demagnetizing factors are dimensionless numbers between 0 and 1."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "All statements are true except a). Demagnetizing fields decrease the apparent magnetic susceptibility of weakly ferromagnetic objects."}}
{"id": "q_STATIC_10", "question": "A person with a steel BB lodged in his eye approaches a 3.0T MR scanner. Assuming the low-carbon steel of which it is made has a saturation value Bsat = 1.5T and because it is spherical, it has a demagnetization factor (N) of 1/3 in each direction, calculate the fringe external field (Bext) where the BB would become magnetically saturated.", "golden_answers": [0], "choices": ["0.5 T", "1.0 T", "1.5 T", "3.0 T"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 4.0, "hint": "The external field which produces magnetic saturation is given by the equation Bext= N • Bsat. For the case of the BB, Bext= 1/3 • 1.5T = 0.5T (answer a)"}}
{"id": "q_STATIC_11", "question": "Which of the following shaped materials would have the largest demagnetizing factor (N) along the direction of the main magnetic field?", "golden_answers": [1], "choices": ["A sphere", "A flat plate facing the main field", "A flat plate parallel to the main field", "An elongated cylinder pointing in the direction of the main field"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 4.0, "hint": "A flat plate oriented en face to the direction of the main field would have virtual poles very close together and hence produce a strong demagnetizing effect. N would therefore be close to 1.0, the maximum possible value for any shaped object, so answer b) is correct."}}
{"id": "q_STATIC_12", "question": "Mathematical analysis of predicted magnetic forces on metal objects often uses models based on", "golden_answers": [2], "choices": ["Spheres", "Long tubes", "Ellipsoids", "Flat sheets"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 4.0, "hint": "Answer c), ellipsoids, is correct. By changing the length, angulation, and diameter parameters, an ellipsoid can be approximately deformed into one of the other shapes. And ellipsoids admit to a closed-form mathematical solution in many cases."}}
{"id": "q_STATIC_13", "question": "Translational force on an unsaturated metal object brought near a cylindrical bore MR scanner is maximal", "golden_answers": [3], "choices": ["When first entering the door of the MR scanner room", "At scanner isocenter in the middle of the bore", "At scanner isocenter at the edge of the bore", "Just inside the edge of the magnet bore opening"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Translational force is proportional to the local field (B) multiplied by its spatial rate of change (dB/dz), a combined entity known as the spatial gradient product (SGP).  The SGP is strongest near the edges of the magnet bore opening, making this the most powerful place for translational forces (answer d is correct). At the magnet isocenter, however, dB/dz ≈ 0, so surprisingly there is no translational force once the object reaches the center of the magnet."}}
{"id": "q_STATIC_14", "question": "The torque on an unsaturated metal object brought near a cylindrical bore MR scanner is maximal", "golden_answers": [3], "choices": ["When first entering the door of the MR scanner room", "At scanner isocenter in the middle of the bore", "At scanner isocenter at the edge of the bore", "Just inside the edge of the magnet bore opening"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "This is a somewhat of a trick question. The answer is actually d), at a location slightly more posterior to the that of the spatial gradient or spatial gradient product. For an unsaturated object, torque is proportional to the square of the magnetic field (B²). So the torque is maximal where B is greatest. Most people assume this is in the center of the scanner, but for cylindrical magnets the local field is perhaps 10-20% higher just inside the bore opening along the inside walls of the scanner.  The correct answer is therefore d), at a location slightly more posterior to the that of the spatial gradient or spatial gradient product maximal where the magnetic field (B) is strongest."}}
{"id": "q_STATIC_15", "question": "Where is the force on an unsaturated metal object the smallest?", "golden_answers": [1], "choices": ["Only exactly at scanner isocenter", "At the majority of places inside the magnet bore where the static field is homogeneous", "Just inside the edge of the scanner bore opening", "One meter from the scanner bore opening"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 4.0, "hint": "The correct answer is b. Translational force is minimized when the spatial gradient (dB/dz) is minimal. Since modern scanners are highly homogeneous, most sites within the main bore of the magnet have dB/dz = 0 and thus produce no translational forces."}}
{"id": "q_STATIC_16", "question": "A steel wrench is inadvertently brought into the room housing a self-shielded 1.5 T scanner. Which statement is true about the magnetic torque on the wrench?", "golden_answers": [1], "choices": ["The torque is maximal when the wrench is held upright and perpendicular to the main magnetic field.", "The torque is maximal when the wrench is tilted at 45º toward the field.", "The torque is maximal when the wrench is turned to be parallel to the field.", "The exact shape or position of the wrench makes no difference on the torque, only its mass."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Answer b) is true. The torque of an unsaturated elongated object depends on sin 2θ, where θ is the angle made with the external field. This is maximal when θ = 45º"}}
{"id": "q_STATIC_17", "question": "When a metal object becomes magnetically saturated by an external field (B), which of the following is false?", "golden_answers": [3], "choices": ["The displacement force is independent of B.", "The displacement force is independent of dB/dz.", "The torque is independent of B.", "The torque is independent of the object’s angulation (θ) with respect to B."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 4.0, "hint": "Only d) is false. Torque remains proportional to sin 2θ but independent of B. Displacement force is independent of both B and dB/dz."}}
{"id": "q_STATIC_18", "question": "The (Spatial Gradient Product) is defined as the (Static Field Strength) times the (Spatial Gradient of the Static Field) at each point in space.  The units of Spatial Gradient Product are", "golden_answers": [3], "choices": ["Tesla", "Tesla/meter", "Tesla/meter²", "Tesla²/meter"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 4.0, "hint": "The static field (T) times the spatial gradient (T/m) gives the units of SGP as T²/m, so answer d) is correct."}}
{"id": "q_STATIC_19", "question": "For a typical cylindrical MR scanner, the location of the maximum Spatial Gradient Product is", "golden_answers": [3], "choices": ["In the middle of the bore at magnet isocenter", "Against the wall of the bore at magnet isocenter", "In the middle of the bore opening", "Along the wall at the bore opening"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 4.0, "hint": "Both the SGP and SG are maximal along the wall of the bore opening and usually quite close together. (Answer d).  This region is would exert the strongest displacement force on a metallic object."}}
{"id": "q_STATIC_20", "question": "A small metallic object is being tested for translational forces by suspending it from a string at the edge of the scanner bore opening using the ASTM method. The hanging object deflects the string by 40º from the vertical. Which of the following conclusions is incorrect?", "golden_answers": [0], "choices": ["The ASTM would state that the risk imposed by magnetic force is no greater than that of the earth’s gravity.", "The ASTM would declare this object to be MR Conditional.", "The ASTM would declare this object to be MR Unsafe.", "The ASTM would declare this object to be MR Safe."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 4.0, "hint": "Because the object did not deflect more than 45º, the deflection force is less than the device’s weight. So by ASTM criteria any risk imposed by the application of the magnetically-induced deflection force is no greater than any risk imposed by normal daily activity in the Earth’s gravitational field. Thus answer a) is correct. The definitions of MR Safe, Unsafe, and Conditional are based on multiple factors (i.e., heating, torque) beyond that available from this simple displacement test."}}
{"id": "q_STATIC_21", "question": "Concerning the Lorentz force, which of the following is true?", "golden_answers": [1], "choices": ["It is the force is experienced by charged particles moving through an electric field.", "It is responsible for T-wave changes on an EKG", "It is responsible for magnetophosphenes and taste disturbances in 7T scanners.", "It is responsible for the stacking up of sickle cell erythrocytes in a magnetic field."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 3.0, "hint": "Only b) is true. This describes the magneto-hydrodynamic (MHD) effect, which is a change in recorded EKG voltages due to displacement of positive and negative ions in the descending aorta due to Lorentz forces. The other choices are false. The Lorentz force is due to particles moving through a magnetic (not electric) field. Magnetophophenes and taste disturbances are due to induced currents per the Faraday-Lenz law. The stacking of sickled red blood cells is a type of susceptibility-induced force."}}
{"id": "q_STATIC_22", "question": "Which of the following concerning MR-related dizziness and vertigo is false?", "golden_answers": [3], "choices": ["It is much more common at 7T than 3T.", "It is likely due to a Lorentz force acting on endolymphic ionic currents.", "It is exacerbated by rapid head or table motion.", "It is most severe and persistent when the patient’s head reaches magnet isocenter."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Answer d) is false. Dizziness/vertigo is typically most severe when the patient is pulled in or out of the magnet bore through the gantry entrance. Once the patient’s head is at isocenter, the vertiginous symptoms and nystagmus decrease after about a minute (unless the patient wiggles her head)."}}
{"id": "q_STATIC_23", "question": "Concerning magnetophosphenes, which statement is false?", "golden_answers": [1], "choices": ["They are much more common at 7T than 3T.", "They are caused by electric field stimulation of the optic nerve.", "Technologists walking around the scanner may experience them.", "They are exacerbated by rapid head or table motion"], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "Answer b) is false. Magnetophosphenes are generated by electric fields of very low frequency and magnitude acting on retinal cells directly, not the optic nerve. The other statements are true."}}
{"id": "q_STATIC_24", "question": "Concerning metallic taste sensations during MRI, which of the following is false?", "golden_answers": [1], "choices": ["Their mechanism of generation is similar to that of magnetophosphenes.", "They are related to release of ions from metallic dental fillings.", "They are much more common at 7T than 3T.", "They are much less common than vertigo or magnetophosphenes."], "metadata": {"subject": "MR Safety and Screening Quiz", "level": 2.0, "hint": "The phenomenon occurs in patients without dental fillings, so answer b) is false."}}
{"id": "q_DIFFQUIZ_00", "question": "The units for the diffusion coefficient (D) are", "golden_answers": [1], "choices": ["mm/sec", "mm²/sec", "mm³/sec", "Dimensionless"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "D reflects the flux of particles through a surface during a certain period of time, it therefore has units of area/time (e.g. mm²/sec)."}}
{"id": "q_DIFFQUIZ_01", "question": "According to the Stokes-Einstein equation, which of the following system changes would increase the diffusion coefficient?  (You should be able to reason this out even if you’ve forgotten the exact equation).", "golden_answers": [0], "choices": ["Increasing temperature", "Increasing viscosity of the medium", "Increasing the size of the particles", "All of the above"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 4.0, "hint": "Increasing temperature increases the kinetic energy and hence motion of the particles, so D is increased. Bigger particles and ones in more viscous media move more slowly, so D is decreased."}}
{"id": "q_DIFFQUIZ_02", "question": "Comparing the diffusion coefficients of water (Dw) and biological tissues (Dt), which statement is most accurate?", "golden_answers": [2], "choices": ["Dw < Dt", "Dw and Dt are almost exactly the same", "Dt is typically only 10-50% of Dw", "Dt is typically less that 1% of Dw"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The diffusion constant for pure water at body temperatures is approximately 3.0 x 10−3 mm2/sec. The values of D for biological tissues are only 10-50% as long, perhaps 1.0 x 10−3mm2/sec on the average."}}
{"id": "q_DIFFQUIZ_03", "question": "How many elements are there in a first-order diffusion tensor for describing anisotropic materials?", "golden_answers": [2], "choices": ["3", "6", "9", "12"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "In anisotropic materials, diffusion cannot be described by a single number, but a [3 x 3] array called the diffusion tensor. The three diagonal elements (Dxx,  Dyy, and (Dzz) of the tensor represent diffusion coefficients measured in the laboratory frame of reference along each of the principal (x-, y- and z-) directions. The six off-diagonal terms (Dxy, Dyz, etc) reflect correlation between random motions corresponding to each pair of principal directions."}}
{"id": "q_DIFFQUIZ_04", "question": "Modern diffusion-weighted pulse sequences all trace their origin to the pulsed gradient spin echo (PGSE) technique developed by", "golden_answers": [0], "choices": ["Stejskal and Tanner", "Solomon and Blombergen", "Carr and Purcell", "Einstein and Stokes"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The pulsed gradient spin echo (PGSE) technique was developed by chemists Edward Stejskal and John Tanner in the mid-1960's. It consisted of paired diffusion sensitizing gradients flanking either side of a 180º-inversion pulse. Modern variations include addition of a chemically selective fat suppression pulses, use of bipolar gradients, and a second 180º pulse immediately before the image acquisition module."}}
{"id": "q_DIFFQUIZ_05", "question": "How can a larger b-value be achieved with paired pulsed diffusion gradients?", "golden_answers": [3], "choices": ["By increasing the amplitude of the gradients", "By increasing the duration of the gradients", "By widening the time interval between the two gradients", "All of the above"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The b-value depends on the strength, duration, and spacing of the pulsed diffusion gradients.  A larger b-value is achieved with increasing the gradient amplitude and duration and by widening the interval between gradient pulses."}}
{"id": "q_DIFFQUIZ_06", "question": "What is the approximate range of b-values used to produce diffusion-weighted images in standard clinical MRI today?", "golden_answers": [2], "choices": ["0 – 10 s/mm²", "0 – 100 s/mm²", "0 – 1,000 s/mm²", "0 – 10,000 s/mm²"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Most routine clinical DWI currently use b-values between 0 and 1000 or perhaps 0 and 2000, with slightly lower values being used outside the central nervous system."}}
{"id": "q_DIFFQUIZ_07", "question": "What are the minimum number of source image gradient directions that must be applied to obtain a diffusion-weighted anatomic image?", "golden_answers": [1], "choices": ["1", "3", "9", "27"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "At least three sets of source images must be obtained. These may be along the laboratory x-, y-, and z-axes or in three arbitrary perpendicular orientations. More modern schemes typically obtain source images in 6, 20 or more directions, but three is the minimum."}}
{"id": "q_DIFFQUIZ_08", "question": "What is the definition of the “trace” of a 3x3 diffusion tensor matrix?", "golden_answers": [2], "choices": ["The largest element", "The sum of all the elements", "The sum of the diagonal elements", "The average of the diagonal elements"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The term \"trace\" comes from matrix algebra where it means the sum of diagonal elements of such an array. The trace of the diffusion tensor equals (Dxx +  Dyy + Dzz)."}}
{"id": "q_DIFFQUIZ_09", "question": "If the trace of a 3x3 diffusion tensor matrix corresponding to a single pixel is calculated to be 1.5 x 10–3 s/mm², what is the corresponding apparent diffusion coefficient (ADC)?", "golden_answers": [0], "choices": ["0.5 x 10–3 s/mm²", "1.5 x 10–3 s/mm²", "3.0 x 10–3 s/mm²", "4.5 x 10–3 s/mm²"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 4.0, "hint": "The apparent diffusion coefficient (ADC) is considered to be the average value of the trace, or ADC = (Dxx +  Dyy + Dzz) / 3."}}
{"id": "q_DIFFQUIZ_10", "question": "Concerning the ADC map, which one of the following statements is true?", "golden_answers": [2], "choices": ["A lesion bright on a trace DWI image will be dark on an ADC map.", "Lesions with very long T2 values will appear dark on an ADC map.", "Normal urine will appear dark on a trace DWI image and bright on an ADC map.", "The ADC map is simply the inverse of the trace DWI image."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The Trace DW image is not a map of diffusion; it is only diffusion-weighted, a fact implicit in its name. Trace DW images possess considerable T2-weighting. As such, lesions with either very long or very short T2 values may \"contaminate\" the Trace DW images, making them appear \"artificially\" bright or dark. These important phenomena are known as \"T2-shine-through\" and \"T2-black-out. T2-effects can be mathematically removed from the DW image to create a pure parametric image of apparent diffusion coefficients (the \"ADC Map\"). The ADC map is not a simple inverse of the DWI trace image."}}
{"id": "q_DIFFQUIZ_11", "question": "Which of the following is incorrect concerning exponential ADC maps?", "golden_answers": [3], "choices": ["eADC maps have a gray scale that parallels that seen in the trace DW images.", "eADC maps are simply the trace DW image divided by the b0 image.", "eADC maps have more noise than trace DW images.", "eADC maps still have the problem of “T2-shine-through”."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The eADC map is simply the trace DW image divided by the b0 image for each point."}}
{"id": "q_DIFFQUIZ_12", "question": "A cerebral hematoma 36-hours-old appears dark on both the b0 and trace DW images.", "golden_answers": [2], "choices": ["Diffusion is not restricted in the hematoma.", "This is an example of “T2-shine-through”.", "This is an example of “T2-blackout”.", "This is an example of diffusion anisotropy."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "This case illustrates the “T2-blackout” phenomenon, where severe T2* shortening (here due to paramagnetic deoxyhemoglobin in the hematoma) spills over and “contaminates” the trace DW images. Diffusion is actually restricted in the hematoma (think of all the clumped red blood cells and fibrin), but appears (falsely) dark on the DW image."}}
{"id": "q_DIFFQUIZ_13", "question": "Which one of the following mechanisms does not explain restricted diffusion in an acute cerebral infarction?", "golden_answers": [1], "choices": ["Increased intracellular water (cytotoxic edema)", "Decreased intracellular and extracellular viscosity.", "Reduction in extracellular space.", "Fragmentation of cellular components."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "All are correct except for (b). As cellular components fragment and proteins unravel, viscosity increases (not decreases). Increased viscosity restricts diffusion because it inhibits the movement of water molecules through the diseased tissue."}}
{"id": "q_DIFFQUIZ_14", "question": "Which of the following tumors would not be expected to demonstrate restricted diffusion?", "golden_answers": [2], "choices": ["Splenic lymphoma", "Cerebellar medulloblastoma", "Pancreatic serous cystadenoma", "Ewing’s sarcoma (PNET) of the pelvis"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Highly cellular neoplasms with densely packed cells and relatively little extracellular space often demonstrate restricted diffusion. Examples include lymphomas, medulloblastomas, primitive neuroectodermal tumors (PNETs) and highly malignant gliomas. A cystic tumor (like option c would not be expected to restrict diffusion."}}
{"id": "q_DIFFQUIZ_16", "question": "How many measurements does it take to determine the unique diffusion tensor elements in the prior question?", "golden_answers": [2], "choices": ["5", "6", "7", "9"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Six measurements need to be taken with the diffusion sensitizing gradients applied, plus one b0 measurement, giving a total of 7."}}
{"id": "q_DIFFQUIZ_17", "question": "Concerning the diffusion ellipsoid, which statement is false?", "golden_answers": [3], "choices": ["The directions of its major and minor axes are described by eigenvectors.", "The radii of its major and minor axes are eigenvalues.", "The eigenvalues are proportional to Einstein’s root mean square diffusion displacement in each direction.", "The diffusion tensor matrix for the diffusion ellipsoid has 6 unique elements."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "A significant benefit to using the diffusion ellipsoid is that in this frame of reference, the off-diagonal elements of the diffusion tensor disappear. The set of eigenvalues define a matrix with only unique 3 diagonal elements (λ1, λ2, and λ3) with the off-diagonal elements all zeroes. Link to Q&A discussion"}}
{"id": "q_DIFFQUIZ_18", "question": "Concerning fractional anisotropy (FA), which statement is incorrect?", "golden_answers": [0], "choices": ["FA varies from −1 to +1.", "FA is an index for the amount of diffusion asymmetry within a voxel.", "FA = 0 for a voxel with perfect isotropic diffusion.", "On an FA map, brighter areas are more anisotropic than darker areas."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The value of FA varies between 0 and +1 (option a is incorrect). For perfect isotropic diffusion, λ1 = λ2 = λ3, the diffusion ellipsoid is a sphere, and FA = 0. With progressive diffusion anisotropy, the eigenvalues become more unequal, the ellipsoid becomes more elongated, and the FA → 1. The FA map is a gray-scale display of FA values across the image. Brighter areas are more anisotropic than darker areas."}}
{"id": "q_DIFFQUIZ_19", "question": "Concerning whole-body DWI, which statement is false?", "golden_answers": [1], "choices": ["Imaging is obtained in multiple blocks or stations, then digitally stitched together.", "Views of the chest and abdomen must be obtained during breath holding to reduce motion artifact.", "Standard image display is in a black-background mode to resemble PET-CT.", "Each DWI sequence is preceded by a STIR-like inversion pulse for fat suppression."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Whole-body DWI does not require breath holding. Even though the organs of the abdomen and chest move during image acquisition, they do so \"coherently\". Their physical displacements are cyclic and while this motion produces some spatial blurring it does not significantly affect the magnitude of the DW signal."}}
{"id": "q_DIFFQUIZ_20", "question": "All of the following are advantages of readout-segmented DWI over single-shot DWI, except", "golden_answers": [1], "choices": ["Increased signal-to-noise", "Decreased imaging time", "Decreased susceptibility artifacts", "Reduced spatial blurring"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Depending on the number of “shots” readout segmented DWI can take 3-5 times longer than single-shot DWI, so option (b) is false."}}
{"id": "q_DIFFQUIZ_21", "question": "The key technological development underlying modern small field-of-view DWI methods (like ZOOMit and FOCUS) is", "golden_answers": [0], "choices": ["Use of 2D spatially-selective composite RF pulses", "Use of outer volume saturation pulses", "Use of stimulated echo inner volume pulses", "Use of extremely strong, continuously applied gradients"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Newer small FOV DWI sequences employ a special 2D RF excitation pulse that is spatially selective in both the slice select and phase-encoding directions. The 2D RF \"pulse\" is a composite of approximately 25 closely spaced \"sub-pulses\" extending over a time frame of about 15 ms. This RF excitation is played out simultaneously with a fast (oscillatory) gradient along the phase-encode axis and a slow (\"blipped\") gradient along slice-select."}}
{"id": "q_DIFFQUIZ_22", "question": "Which of the following statements about intravoxel incoherent motion (IVIM) is true?", "golden_answers": [1], "choices": ["IVIM effects are most easily recognized when high b-values are used.", "IVIM describes signal losses due to both diffusion and microscopic perfusion.", "IVIM perfusion effects mitigate the signal losses caused by diffusion alone.", "Le Bihan’s IVIM model allows estimation of capillary blood flow."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The correct statement is (b): IVIM describes signal losses due to both diffusion and microscopic perfusion. If the gradients are relatively strong, IVIM-induced signal losses are primarily due to diffusion — the Brownian motion of water molecules in and around cells. When weaker gradients are used, however, a second IVIM mechanism also contributes to signal loss — microcirculation of blood in the capillary network. Le Bihan’s IVIM model allows estimation of the perfusion fraction (the percent of a voxel volume occupied by capillaries), but not the blood flow through them."}}
{"id": "q_DIFFQUIZ_23", "question": "Which of the following statements about diffusion kurtosis is false?", "golden_answers": [2], "choices": ["Diffusion kurtosis measures the non-Gaussian movement of water molecules.", "Kurtosis effects are more noticeable when long echo times are used.", "Kurtosis effects are more noticeable when low b-values are used.", "The mean kurtosis (K) of a pure fluid is zero."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Standard diffusion weighted imaging (DWI) methods have incorporated Einstein's original concept that the diffusion water molecules follows a Gaussian (normal) distribution. Non-Gaussian behavior becomes more noticeable when stronger gradients (higher b-values) and longer echo times are used.  By definition, a Gaussian distribution has K = 0, which would be the case with a pure fluid."}}
{"id": "q_FWQUIZ_00", "question": "What is the main type of fat within the body which contributes most to the signal recorded on MRI?", "golden_answers": [0], "choices": ["Triglycerides", "Free fatty acids", "Cholesterol", "Phospholipids"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The bulk of the MR signal in fatty human tissues arises from triglycerides, with lesser contributions from free fatty acids and cholesterol (when esterified or in a semi-solid or liquid state)."}}
{"id": "q_FWQUIZ_01", "question": "At a given field strength, how do the nuclear precession frequencies of ¹H protons differ between fat and water?", "golden_answers": [2], "choices": ["Fat and water protons precess at the same frequency", "Fat protons precess faster than water protons.", "Fat protons precess slower than water protons.", "Fat protons may precess either faster or slower depending on their location along the triglyceride side chains."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "The H protons of triglycerides are nestled within long carbon chains, shielded by electron clouds and protected from the full force of the externally applied magnetic field. In water, by comparison, the electronegative O atom pulls protective electron clouds away from the H nuclei, exposing them to the full force of the external magnetic field. Thus water protons resonate faster than fat protons."}}
{"id": "q_FWQUIZ_02", "question": "A chemical shift of 3.5 ppm written in decimal form is", "golden_answers": [1], "choices": ["0,00000035", "0,0000035", "0,000035", "0,00035"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The abbreviation ppm stands for “parts per million” and is equivalent to multiplying the base value by 10−6. So 3.5 ppm = 3.5 x 10−6 = 0.0000035 (answer b)."}}
{"id": "q_FWQUIZ_03", "question": "If the water-fat chemical shift is 3.5 ppm, calculate the fat-water frequency difference for a 7T scanner operating at 200 MHz.", "golden_answers": [2], "choices": ["220 Hz", "440 Hz", "700 Hz", "900 Hz"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 4.0, "hint": "Δf = (200 MHz)(3.5 ppm) = (200 x 106 Hz)(3.5 x10−6) ≈ 700 Hz"}}
{"id": "q_FWQUIZ_04", "question": "If the water-fat chemical shift is 3.5 ppm, calculate the water-fat frequency difference for a portable 0.064T scanner operating at 150 kHz.", "golden_answers": [0], "choices": ["0.5 Hz", "5 Hz", "50 Hz", "500 Hz"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 4.0, "hint": "Δf = (150 kHz)(3.5 ppm) = (150 x 103 Hz)(3.5 x10−6) ≈ 0.5 Hz. This very low frequency separation means that water-fat artifacts will be minimal at this field strength, and also that spectral fat suppression methods cannot be used.  Link to Q&A discussion"}}
{"id": "q_FWQUIZ_05", "question": "At 1.5 T water and fat go in and out of phase about every 2.2 msec. How fast would they go in and out of phase at 3.0T?", "golden_answers": [0], "choices": ["Every 1.1 msec", "Every 2.2 msec", "Every 3.3 msec", "Every 4.4 msec"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "The period of this phase cycling is 1/Δf, where Δf is the frequency offset between the spins. So if the field is doubled, the frequency offset is twice as large, and the phase cycling period is half as large, so (a) 1.1 msec is the correct answer."}}
{"id": "q_FWQUIZ_06", "question": "An adrenal mass that is of intermediate signal intensity on an in-phase image and low signal on an out-of-phase image is most likely an", "golden_answers": [1], "choices": ["Adrenal carcinoma", "Adrenal adenoma", "Adrenal metastasis", "Adrenal pheochromocytoma"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Adrenal adenomas, the most common tumor of the adrenal gland, often contain microscopic lipid droplets. Voxels containing both lipid and water result in signal cancellation with low signal on out-of-phase GRE images."}}
{"id": "q_FWQUIZ_07", "question": "Which of the following is not one of the four standard images produced by most commercial Dixon-type sequences?", "golden_answers": [0], "choices": ["Chemical shift", "Water", "Fat", "In-phase"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Choice (a), chemical shift, is not a standard image generated by a Dixon sequence. The other four are."}}
{"id": "q_FWQUIZ_08", "question": "Concerning CHESS/Fat-Sat pulses, which one of the following statements is incorrect?", "golden_answers": [3], "choices": ["They reduce the number of available slices for a given TR.", "They cause tissue heating.", "They include a spectrally tuned RF-pulse followed by spoiler gradients along one or more axes.", "They are the preferred method for fat suppression at 0.3T and below."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "All are correct except choice (d). The effectiveness of a Fat-Sat pulse depends primarily on field strength and field homogeneity. At fields below 0.3T the water and fat peaks are so close together (in Hz) that it is difficult to cleanly suppress one or the other with a chemically selective pulse. At low fields another method of fat suppression (typically STIR or Dixon) must therefore be used."}}
{"id": "q_FWQUIZ_09", "question": "Which of the following flip angle patterns would not be considered to define a composite binomial pulse for water excitation?", "golden_answers": [1], "choices": ["1:1", "0,04237268519", "0,04306712963", "1:3:3:1"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 4.0, "hint": "Binomial pulses are typically used for selective water excitation as a means of fat suppression. Binomial pulses have flip angles that follow the pattern of coefficients of the binomial expansion of (a+b)n: 1-1, 1-2-1, 1-3-3-1, etc. Thus, a 90º-pulse could be constructed as a [45º-45º] pair, a [22.5º-45º-22.5º] triplet, or a [11.25º-33.75º-33.75º-11.25º] quadruplet. So choice (b), 1:1:1 is not a binomial pulse."}}
{"id": "q_FWQUIZ_10", "question": "Limitations of the STIR technique for fat suppression include all except", "golden_answers": [3], "choices": ["Inability to use it to detect gadolinium enhancement.", "Suppression of other short T1 materials besides fat (eg, protein, blood).", "Tissue heating from multiple 180º pulses.", "Decreased visualization of long T1/long T2 lesions due to competitive signal effects."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "All are valid limitations except for (d), which is incorrect. In routine SE imaging lesions with prolonged T1 and T2 have competitive effects on signal intensity (↑T1 reduces signal while ↑T2 increases signal). In STIR imaging the effects of ↑T1 and ↑T2 are additive, allowing for improved visualization of some lesions, such as multiple sclerosis plaques."}}
{"id": "q_FWQUIZ_11", "question": "The Spectral Presaturation with Inversion Recovery (SPIR) technique can be thought of as a hybrid combining fat suppression features of", "golden_answers": [0], "choices": ["Spectral Fat Sat (CHESS) + STIR", "Dixon Technique + STIR", "Spectral Fat Sat (CHESS) + Selective Water excitation", "Dixon Technique + Selective Water excitation"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "SPIR is a hybrid technique that combines a fat-selective RF-pulse and spoiler gradient (similar to CHESS) together with nulling of the residual longitudinal fat magnetization through an inversion delay mechanism (similar to STIR). These spin manipulations purely involve fat; the water resonance is unaffected. After a suitable inversion time to null residual fat signal, any pulse sequence can be used to image the remaining water."}}
{"id": "q_FWQUIZ_12", "question": "Which of the following statements comparing SPAIR (SPectral Attenuated Inversion Recovery) and SPIR (Spectral Presaturation with Inversion Recovery) is incorrect?", "golden_answers": [2], "choices": ["SPAIR uses adiabatic pulses while SPIR does not.", "SPAIR uses an inversion pulse of 180º, while SPIR uses pulses in the 100º -120º range", "SPAIR deposits less RF energy into tissue than does SPIR.", "The inversion time is longer for SPAIR than SPIR."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Both SPAIR and SPIR can be thought of as CHESS-STIR hybrids. SPAIR uses 180º adiabatic pulses while SPIR uses non-adiabatic pulses in the 100º -120º range. Accordingly-SPAIR pulses deposit more RF-energy in tissue than the smaller flip angle SPIR or CHESS pulses. The inversion time is longer in SPAIR than SPIR, so there is a greater penalty in terms of imaging time and reduced number of slices for a given TR."}}
{"id": "q_FWQUIZ_13", "question": "Which of the following statements about adiabatic RF-pulses is false?", "golden_answers": [3], "choices": ["They are both amplitude- and frequency-modulated.", "Their transmitted frequency changes simultaneously with amplitude as the pulse evolves.", "They are less sensitive to B1 inhomogeneities that other pulses.", "They are commonly used in low-field applications."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Only (d) is false. Like other non-adiabatic but spectrally selective pulses (CHESS, STIR) they can only be used at higher, rather homogeneous fields where there is a clean separation of water and fat resonances Link to Q&A discussion"}}
{"id": "q_GRADSUS_00", "question": "Which of the following is not an advantage of gradient echo imaging over spin-echo imaging?", "golden_answers": [3], "choices": ["Shorter TEs", "Shorter TRs", "Reduced flow artifacts", "Reduced susceptibility artifacts"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Phase shifts resulting from magnetic field inhomogeneities, static tissue susceptibility gradients, or chemical shifts are not cancelled at the center of the GRE as they are in SE sequences.  Image contrast is therefore dictated not by true T2-relaxation, but by these other factors which constitute T2*. GRE sequences are therefore more frequently troubled by susceptibility and chemical shift artifacts and do not function well on scanners whose magnetic fields lack homogeneity Link to Q&A discussion"}}
{"id": "q_GRADSUS_01", "question": "Concerning multi-echo GRE, which statement is true?", "golden_answers": [2], "choices": ["The peak value of successive echoes is determined by the T2 decay of the tissue imaged.", "The peak value of successive echoes echo is determined by the T1 value of the tissue imaged.", "One common application is for fat-water imaging.", "Each successive echo must be preceded by its own RF-pulse."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The peak value of successive echoes is determined by the T2* decay (not T2 decay) of the tissue imaged (options a and b are false). One common application of multi-echo GRE is for acquiring fat-water \"in-phase\" and \"out-of-phase\" images using two different TE's (options c is true). Only one RF pulse is used for the entire chain of echoes (option d is false)."}}
{"id": "q_GRADSUS_02", "question": "Which is not a technique for gradient echo spoiling?", "golden_answers": [0], "choices": ["Use of very short TR", "Use of 2D multislice mode", "Use of a variable spoiler gradient", "Semirandom phase change of the RF-carrier wave"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "All are valid spoiling methods except choice (a). Long TR values produce “natural” spoiling, not short TRs.  When TR>>T2*, the transverse magnetization will naturally decay to zero by the end of the cycle.  Thus any gradient echo sequence using TR values of several hundred milliseconds will no longer have appreciable transverse coherences and be “spoiled”."}}
{"id": "q_GRADSUS_03", "question": "A spoiled GRE sequence with TR = 10, TE = 3, and α = 50º would be considered primarily", "golden_answers": [0], "choices": ["T1-weighted", "T2-weighted", "T2*-weighted", "Proton-density-weighted"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Short TR and large α accentuate T1-weighted imaging."}}
{"id": "q_GRADSUS_04", "question": "A spoiled GRE sequence with TR = 1000, TE = 30, and α = 5º would be considered primarily", "golden_answers": [2], "choices": ["T1-weighted", "T2-weighted", "T2*-weighted", "Proton-density-weighted"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Long TR and small α minimize T1 weighting, while long TE accentuates T2* weighting."}}
{"id": "q_GRADSUS_05", "question": "A spoiled GRE sequence with TR = 1000, TE = 2, and α = 5º would be considered primarily", "golden_answers": [3], "choices": ["T1-weighted", "T2-weighted", "T2*-weighted", "Proton-density-weighted"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Long TR and small α minimize T1 weighting, while short TE minimizes T2* weighting. This leaves the image more proton-density weighted than the other examples."}}
{"id": "q_GRADSUS_06", "question": "In a spoiled GRE sequence, a low flip angle (α)", "golden_answers": [0], "choices": ["Minimizes T1 weighting", "Accentuates T1 weighting", "Minimizes T2* weighting", "Minimizes proton density weighting"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Flip angle (α) controls T1-weighting. A small flip angle minimizes T1-weighting because the longitudinal magnetizations of various tissues are not differentiated much by such a small angular displacement. Hence at small flip angles, [H] and T2* effects predominate. Conversely, as α → 90º, T1-weighting increases."}}
{"id": "q_GRADSUS_07", "question": "In a spoiled GRE sequence, a long TE", "golden_answers": [1], "choices": ["Maximizes T2 weighting", "Maximizes T2* weighting", "Minimizes T2 weighting", "Minimizes T2* weighting"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "T2*-weighting increases as TE is prolonged. This is because a longer TE allows more time for dephasing before echo formation."}}
{"id": "q_GRADSUS_08", "question": "Which of the following SSFP pulse sequences is considered “balanced”?", "golden_answers": [0], "choices": ["TrueFISP/FIESTA", "FISP/GRASS/FFE", "DESS/MENSA", "PSIF/T2-FFE"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Sequences such as TrueFISP (Siemens) and FIESTA (GE) sample both FID-like and Echo-like SSFP signals and are considered “balanced”."}}
{"id": "q_GRADSUS_09", "question": "Which of the following is not a condition for a SSFP signal to exist?", "golden_answers": [0], "choices": ["TR must be longer than T2.", "Phase shifts caused by gradients must be constant from cycle to cycle.", "Field inhomogeneities must be static.", "Spins must be stationary or motion-compensated."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Choice (a) is incorrect. TR must be significantly shorter (not longer) than T2, or else natural decay processes will destroy the transverse coherence."}}
{"id": "q_GRADSUS_10", "question": "Concerning “coherent” gradient echo sequences like GRASS/FISP, which statement is false?", "golden_answers": [2], "choices": ["If TR is long compared to T2*, the contrast resembles that of a spoiled GRE sequence.", "TE controls T2* weighting.", "Small flip angles (α) produce T1-weighted images.", "Large flip angles produce images that are weighted by T2/T1."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Choice (c) is incorrect. A small flip angle minimizes T1-weighting because the longitudinal magnetizations of various tissues are not differentiated much by such a small angular displacement. Hence at small flip angles, [H] and T2* effects predominate."}}
{"id": "q_GRADSUS_11", "question": "An important tissue weighting present in balanced SSFP sequences like True FISP and FIESTA is", "golden_answers": [3], "choices": ["T1", "T2*", "T1 + T2", "T2/T1"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "True FISP sequences behave more like spin echo than gradient echo sequences in that they do not have T2*-dependence. Also, since TR is nearly always much, much shorter than T1 or T2, the signal intensity is related to the ratio T2/T1."}}
{"id": "q_GRADSUS_12", "question": "Excluding fluids (like urine, blood, and CSF), which of the following tissues is the brightest on balanced SSFP sequences like True FISP and FIESTA?", "golden_answers": [0], "choices": ["Fat", "Myocardium", "Liver", "Brain"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Fat is the second brightest tissue on balanced SSFP images after pure fluids."}}
{"id": "q_GRADSUS_13", "question": "What is the explanation for the brightness of fluid and the tissue identified in the prior question?", "golden_answers": [2], "choices": ["The T2 values are long.", "The T2* values are long.", "The T2/T1 ratios are large.", "The T1+T2 values are large."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Balanced SSFP sequences have the special property that their contrast is dependent not on just T1 or T2, but the ratio T2/T1. For most solid tissues, T1>>T2 so the T2/T1 ratio is small (< 0.10). The exceptions are fat (T2/T1 ≈ 0.30, due to its short T1) and fluids (T2/T1 ≈ 0.70, due to the fact that T1 and T2 are approximately equal)."}}
{"id": "q_GRADSUS_15", "question": "Which of the following statements about DESS (dual-echo steady state) is false?", "golden_answers": [1], "choices": ["Its main use is in musculoskeletal imaging.", "It is insensitive to motion.", "FID-like and Echo-like signal components are recorded separately during a single TR interval.", "Fluids are very bright while trabecular bone is very dark."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "By means of a prolonged and unbalanced readout gradient, DESS generates the FID-like and Echo-like signals from the steady-state free precession individually. It then combines the signals on a pixel-by-pixel basis. DESS is very sensitive to motion, so option (b) is false."}}
{"id": "q_GRADSUS_16", "question": "Which of the following statements about the GRASE (Gradient and Spin Echo) pulse sequence is true?", "golden_answers": [2], "choices": ["It is a widely used sequence for routine head imaging.", "Its tissue energy deposition (specific absorption rate) is higher than with conventional spin echo sequences.", "It is superior to conventional spin echo (CSE) or fast spin echo (FSE) for detecting calcifications and hemorrhages.", "It is primarily used to generate T1-weighted images."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "GRASE is a hybrid technique supposedly combines the best features of CSE and GRE imaging. The GRE contribution makes it useful for detecting calcification of blood (although less so than a pure GRE sequence). Its SAR is lower than a comparable fast spin-echo sequence because there are fewer RF-pulses. GRASE has never achieved much popularity as an imaging method."}}
{"id": "q_GRADSUS_17", "question": "The SI unit for magnetic susceptibility (χ)", "golden_answers": [3], "choices": ["Tesla", "Oersted", "Ampere-meter", "Dimensionless"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Magnetic susceptibility,  denoted by the Greek letter chi (χ), is defined as the magnitude of the internal polarization (J) divided by the strength of the external field (B). Since it is the ratio of two magnetic fields, susceptibility is a dimensionless number."}}
{"id": "q_GRADSUS_18", "question": "Concerning diamagnetism, which statement is false?", "golden_answers": [1], "choices": ["The internal magnetization/polarization of a diamagnetic substance opposes the applied field.", "Diamagnetic substances have positive susceptibilities (χ > 0).", "Water, and hence most tissues, are diamagnetic.", "Calcifications are diamagnetic."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Diamagnetic substances become polarized in a manner that opposes the applied magnetic field. They have negative, not positive, susceptibilities (option b is false). Water, calcifications, and most tissues are diamagnetic."}}
{"id": "q_GRADSUS_19", "question": "Concerning paramagnetism, which statement is false?", "golden_answers": [3], "choices": ["The internal magnetization/polarization of a paramagnetic substance is in the same direction as the applied field.", "Air is paramagnetic.", "Gadolinium contrast material is paramagnetic.", "Most steels are paramagnetic."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Paramagnetic substances become polarized in a manner that augments the applied magnetic field. They have positive susceptibilities. Surprisingly, molecular oxygen is mildly paramagnetic, so air is as well. Gadolinium contrast is paramagnetic. Most steels are ferromagnetic, a phenomenon resembling, but many orders of magnitude greater than paramagnetism."}}
{"id": "q_GRADSUS_20", "question": "Which of the following 2D gradient echo sequences would be most useful for demonstrating small calcifications or hemorrhages in the brain?", "golden_answers": [0], "choices": ["TR = 800, TE = 30, α = 20°", "TR = 2000, TE = 10, α = 70°", "TR = 60, TE = 3, α = 45°", "TR = 800, TE = 10, α = 45°"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Hemorrhage/calcification GRE sequences are characteristically operated in 2D multi-slice mode using relatively long TR's and low flip angles (both minimizing T1 effects) and relatively long TE's (to accentuate T2* dependence). So choice (a) is the best answer."}}
{"id": "q_GRADSUS_21", "question": "Concerning susceptibility-weighted imaging (SWI), which of the following is false?", "golden_answers": [2], "choices": ["SWI images are typically acquired in 3D rather than 2D mode.", "Magnitude and phase information can be individually viewed or combined.", "SWI imaging is inferior to 3D GRE studies for detecting microhemorrhages and calcifications.", "SWI studies typically include minimum intensity images."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Multiple studies have shown that SWI imaging is superior to 3D GRE studies for detecting microhemorrhages and calcifications."}}
{"id": "q_GRADSUS_22", "question": "Concerning SWI phase map images, which statement is incorrect?", "golden_answers": [1], "choices": ["A lesion that is bright on a GE scanner will appear dark on a Siemens scanner.", "Phase map images are displayed using a minimum intensity projection algorithm.", "If a venous sinus appears dark on a phase image, paramagnetic blood products will also be dark.", "The choroid plexus and pineal gland provide a good internal reference for diamagnetic substances."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Phase map images are rendered in a simple magnitude mode on a slice-by-slice basis, so option (b) is false. The \"colors\" (black or white) of diamagnetic and paramagnetic substances on SWI phase images are scanner- dependent, so reference to a known tissue (veins for paramagnetic, choroid plexus calcification for diamagnetic) are needed as an internal check."}}
{"id": "q_MRSIGNALS_00", "question": "The MR signal generated by a single RF-pulse is called a", "golden_answers": [0], "choices": ["Free induction decay (FID)", "Spin echo (SE)", "Gradient echo (GRE)", "Stimulated echo (STE)"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The FID is produced by a single RF-pulse as the tipped nuclear magnetization precesses around Bo and generates current in the receiver coil via induction (Faraday-Lenz Law)."}}
{"id": "q_MRSIGNALS_01", "question": "Concerning the FID, which of the following is true?", "golden_answers": [1], "choices": ["It oscillates indefinitely at the resonance frequency", "It decays with time constant T2*", "It increases in amplitude with time constant T1", "It is generated by a perfect 180º pulse"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The FID is a damped sinusoidal oscillation at the resonance frequency that decays with time constant T2*."}}
{"id": "q_MRSIGNALS_02", "question": "If a magnetic field gradient is turned on immediately after an RF pulse, what happens to the MR signal?", "golden_answers": [2], "choices": ["It becomes a free induction decay (FID)", "It remains unchanged", "It dies out quickly", "It becomes refocused into a gradient echo (GRE)"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The initial MR signal is already synonymous with the FID (choice a is false). Turning on a gradient during the FID causes it to decay more quickly than it would by T2* processes alone (choice c is correct). A second, later applied gradient with opposite polarity is required to generate a GRE."}}
{"id": "q_MRSIGNALS_03", "question": "Another name for a gradient echo is a", "golden_answers": [0], "choices": ["Field echo", "RF echo", "Spin echo", "Stimulated echo"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 1.0, "hint": "Less commonly used, field echo (FE) is the correct answer. Some manufacturers, including Philips and Canon, use FE or FFE (fast field echo) to name their gradient echo sequences. Another synonym is gradient-recalled echo (GRE)."}}
{"id": "q_MRSIGNALS_04", "question": "What happens if a gradient is turned on after the FID has spontaneously decayed?", "golden_answers": [3], "choices": ["A gradient recalled echo is produced.", "A spin echo is produced.", "The FID is partially regenerated.", "Nothing."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Once the FID has spontaneously decayed by T2* processes, no signal can be recovered by action of a gradient."}}
{"id": "q_MRSIGNALS_05", "question": "The first lobe of a gradient applied during a simple GRE imaging sequence is called the", "golden_answers": [1], "choices": ["Readout gradient.", "Dephasing gradient.", "Rephasing gradient.", "Bipolar gradient."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "The first step in a GRE sequence is to dephase the FID, so this lobe is referred to as the “dephasing gradient”.  The dephasing gradient results in accelerated dephasing beyond normal T2* processes with 'squelching/ scrambling' of the FID."}}
{"id": "q_MRSIGNALS_06", "question": "The rephasing gradient refocuses spins that have been dephased by", "golden_answers": [0], "choices": ["The dephasing gradient only", "T2 only", "T2* only", "The dephasing gradient, T2, and T2*"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The rephasing gradient only refocuses spins scrambled by the dephasing gradient itself. T2 and T2* processes are unaffected and contribute to continued signal loss  Link to Q&A discussion"}}
{"id": "q_MRSIGNALS_07", "question": "Spin echoes were first described by", "golden_answers": [3], "choices": ["Felix Bloch", "Edward Purcell", "Isador Rabi", "Erwin Hahn"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "Erwin Hahn discovered spin echoes while a graduate student in 1949."}}
{"id": "q_MRSIGNALS_08", "question": "A single spin echo is produced by", "golden_answers": [2], "choices": ["A single RF-pulse", "A single RF-pulse plus gradient reversal", "Two RF-pulses", "Three RF-pulses"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "A single RF pulse generates a free induction decay (FID), but two successive RF pulses produce a spin echo (SE)."}}
{"id": "q_MRSIGNALS_09", "question": "In a spin echo pulse sequence, the time between the middle of the first RF-pulse and the peak of the spin echo is", "golden_answers": [1], "choices": ["TR", "TE", "TE/2", "TI"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "The time between the middle of the first RF pulse and the peak of the spin echo is called the echo time (TE)."}}
{"id": "q_MRSIGNALS_10", "question": "In a spin echo pulse sequence, the time between the first and second RF-pulses is", "golden_answers": [2], "choices": ["TR", "TE", "TE/2", "TI"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The spin echo occurs at time TE, which is twice the interpulse spacing. So the correct answer is TE/2 Link to Q&A discussion"}}
{"id": "q_MRSIGNALS_11", "question": "Spin-echoes for imaging are often produced using a 90º-pulse followed by a 180º-pulse. What would happen if the second pulse were changed to 90º?", "golden_answers": [2], "choices": ["No echo would be produced.", "A normal sized echo would be produced at a time 2 x TE", "An echo half as large would be produced at time TE", "An echo half as large would be produced at time 2 x TE"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "A 90º-90º RF pair was what Erwin Hahn originally used, and the resultant echo is often known as a Hahn echo.  A Hahn echo will be formed from any two arbitrary RF pulses at time TE, with magnitude reduced depending on the angles chosen. The maximum SE intensity of a 90°-90° pair is only half as large as that produced by a 90°-180° pair."}}
{"id": "q_MRSIGNALS_12", "question": "Which spin-echo pulse pair would be expected to produce the largest signal?", "golden_answers": [1], "choices": ["90º-90º", "90º-180º", "180º-90º", "180º-180º"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "The reason 90°-180° pairs are most commonly used is that this combination produces the maximum possible echo signal. The maximum SE intensity of a 90°-90° pair is only half as large as that produced by a 90°-180° pair. In general, if the first RF-pulse has flip angle α1 and the second has flip angle α2, the maximum signal intensity of the Hahn echo will be smaller than the conventional (90°-180°) echo by a factor of  (sin α1)•(sin² α2/2)."}}
{"id": "q_MRSIGNALS_14", "question": "Of these, how many are considered to be “stimulated” echoes?", "golden_answers": [0], "choices": ["1", "2", "None of them", "All of them"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Only 1 stimulated echo is produced by 3 RF pulses."}}
{"id": "q_MRSIGNALS_15", "question": "A sample placed in a static magnetic field develops an initial longitudinal magnetization Mo. It is then subjected to series of RF-pulses equally spaced apart by time TR. If TR>>T1, what can be said about Mz, the longitudinal magnetization immediately before each subsequent RF-pulse?", "golden_answers": [1], "choices": ["It cannot be predicted.", "It is the same as Mo.", "It is larger than Mo.", "It is smaller than Mo."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "If TR is sufficiently long (the usual requirement is TR > 4-5x T1), the longitudinal magnetization will have time to completely recover and be restored to its full initial magnetization Mo at the time of the next RF-pulse."}}
{"id": "q_MRSIGNALS_16", "question": "A sample placed in a static magnetic field develops an initial longitudinal magnetization Mo. It is then subjected to series of RF-pulses equally spaced apart by time TR. If T2* < TR < T1, what can be said about Mz, the longitudinal magnetization immediately before each subsequent RF-pulse?", "golden_answers": [3], "choices": ["It cannot be predicted.", "It is the same as Mo.", "It is larger than Mo.", "It is smaller than Mo."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "In this scenario, TR is now the same or shorter than T1. Here the second and subsequent pulses occur before the longitudinal magnetization has returned to its initial value (Mo). After a few pulses a new steady-state longitudinal magnetization (Mss) will be established, where Mss) < Mo."}}
{"id": "q_MRSIGNALS_17", "question": "The above situation (in Question 17) is known as", "golden_answers": [0], "choices": ["Partial saturation", "Complete saturation", "Steady-state free precession", "Incomplete magnetic equilibrium"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "This phenomenon is called partial saturation, meaning that the spin system has not fully relaxed back to its equilibrium condition."}}
{"id": "q_MRSIGNALS_18", "question": "A sample placed in a static magnetic field develops an initial longitudinal magnetization Mo. It is then subjected to series of RF-pulses equally spaced apart by time TR. If T2* < TR < T1, what can be said about Mxy, the transverse magnetization, midway between subsequent RF-pulses?", "golden_answers": [3], "choices": ["It cannot be predicted.", "It is the same as Mo.", "It is smaller than Mo but not zero.", "It is zero."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The sample is partially saturated, as noted in question #17, reaching a new non-zero steady-state longitudinal magnetization, Mss) < Mo. But because TR > T2*, complete decay of the transverse magnetization occurs midway between each pair of RF-pulses, so the answer is zero (d)."}}
{"id": "q_MRSIGNALS_21", "question": "If the initial longitudinal magnetization of a sample is Mo, what is the longitudinal magnetization immediately after a 90º-pulse?", "golden_answers": [3], "choices": ["Mo", "−Mo", "½ Mo", "Zero"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "After an ideal 90º-pulse the longitudinal magnetization should be zero."}}
{"id": "q_MRSIGNALS_22", "question": "If the initial longitudinal magnetization of a sample is Mo, what is the transverse magnetization immediately after a 90º-pulse?", "golden_answers": [0], "choices": ["Mo", "−Mo", "½ Mo", "Zero"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "After an ideal 90º-pulse all the longitudinal magnetization should be converted to transverse."}}
{"id": "q_MRSIGNALS_23", "question": "If the initial longitudinal magnetization of a sample is Mo, what are the longitudinal (Mz) and transverse (Mz) magnetizations", "golden_answers": [1], "choices": ["About 90% of Mo", "About 70% of Mo", "About 50% of Mo", "About 10% of Mo"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "From trigonometric identities we see that when a magnetization vector initially aligned with the z-axis is flipped by angle α, the transverse and longitudinal components of magnetization after the flip will be [Mo"}}
{"id": "q_MRSIGNALS_24", "question": "The flip angle that maximizes MR signal from a tissue in a GRE sequence without transverse coherences is known as the", "golden_answers": [3], "choices": ["Hahn angle", "Bloch angle", "Purcell angle", "Ernst angle"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 4.0, "hint": "Named after Richard R. Ernst, who received the Nobel Prize in Chemistry in 1991 for his discovery."}}
{"id": "q_MRSIGNALS_25", "question": "When is the Ernst (optimal flip) angle approximately equal to 90º?", "golden_answers": [0], "choices": ["When TR >> T1", "When TR ≈ T1", "When TR << T1", "Never"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 4.0, "hint": "The Ernst angle (αE) can be calculated from the equation, αE = arccos (e−TR/T1). It reaches its maximum of 90º only when TR >> T1."}}
{"id": "q_SEIR_00", "question": "In a spin-echo pulse sequences the 180°-pulse refocuses spins dephased by", "golden_answers": [0], "choices": ["Magnetic field inhomogeneities", "Diffusion", "T2 processes", "All of the above"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "The 180°-pulse allows refocusing of nonmoving spins whose phases have been scattered by constant field distortions and inhomogeneities. The pulse does not correct for T1 or true T2 effects due to random processes at the atomic/molecular level. It does not correct for phase shifts of spins that move, flow, diffuse or undergo chemical exchange."}}
{"id": "q_SEIR_01", "question": "Comparing Multi-echo Spin Echo (MSE) and Fast (Turbo) Spin Echo (FSE), which of the following statements is false?", "golden_answers": [3], "choices": ["Both MSE and FSE use more than one 180°-pulses during each TR interval.", "MSE uses only one phase-encoding gradient during each TR interval.", "FSE applies the phase-encoding gradient multiple times during each TR interval.", "The echo amplitude decreases with successive 180°-pulses in both MSE and FSE imaging."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "In FSE different phase-encoding gradients are being applied with each 180°-pulse, so the amplitude of the echo may vary depending on the phase-encode step.  In MSE the phase-encoding gradient is turned on only once in each TR interval, so successive echoes become reduced in signal intensity."}}
{"id": "q_SEIR_02", "question": "Which of the following spin-echo parameter selections would produce a proton-density-weighted image?", "golden_answers": [2], "choices": ["TR = 500, TE = 10", "TR = 500, TE = 100", "TR = 5000, TE = 10", "TR = 5000, TE = 100"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 1.0, "hint": "Answer c), a long TR and short TE are used to produce a proton-density-weighted image."}}
{"id": "q_SEIR_03", "question": "A spin-echo sequence using a short TR and long TE produces", "golden_answers": [3], "choices": ["A T1-weighted image", "A T2-weigthed image", "A PD-weighed image", "A noisy low contrast image"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "The correct answer is d). So this combination is seldom used."}}
{"id": "q_SEIR_04", "question": "Tissues or lesions with long values of T1 and T2 are typically", "golden_answers": [1], "choices": ["Bright on T1-weighted SE images", "Bright on T2-weighted SE images", "Bright on both T1- and T2-weighted SE images", "Dark on both T1- and T2-weighted SE images"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Such lesions are typically bright on T2-weighted images and dark on T1-weighted images."}}
{"id": "q_SEIR_06", "question": "In the Inversion Recovery (IR) spin-echo pulse sequence, the inversion time (TI) is defined as", "golden_answers": [0], "choices": ["The time between the first 180°-pulse and first 90°-pulse", "The time between the first 180°-pulse and the echo", "The time between the two 180°-pulses in each TR interval", "The time between the first 90°-pulse and second 180°-pulse"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Answer a) is the definition of TI.  Link to Q&A discussion"}}
{"id": "q_SEIR_07", "question": "Advantages of IR techniques include", "golden_answers": [2], "choices": ["Shorter scan times", "Decrease in flow-related artifacts", "Additive T1 and T2 contrast", "Lower specific absorption rate (SAR)"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "In conventional SE imaging combined T1 and T2 effects are generally competitive, meaning that ↑T1 generally results in decreased signal intensity while ↑T2 results in increased intensity.  In IR imaging by the appropriate choice of TR, T1 and T2 effects can be separated and made to be additive."}}
{"id": "q_SEIR_08", "question": "On a magnitude-reconstructed IR image obtained at 1.5 T, which inversion time would be useful for suppressing fat?", "golden_answers": [0], "choices": ["TI = 170", "TI = 450", "TI = 980", "TI = 2000"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "For most tissues the null point typically occurs when TI ≈ 0.69 x T1.  For fat with a T1 value at 1.5 T of approximately 250, this corresponds to a TI of approximately 170 ms."}}
{"id": "q_SEIR_09", "question": "Which of the following statements concerning phase-sensitive inversion recovery (PSIR) is false?", "golden_answers": [1], "choices": ["Short T1 tissues always have a signal brighter than long T1 tissues, regardless of TI.", "Background air always appears black.", "Selective nulling of tissues by adjusting TI is not possible as it is for magnitude-reconstructed IR.", "It is useful for assessing pediatric myelination and myocardial contrast enhancement."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Phase-sensitive IR preserves the information about the polarity of the longitudinal magnetization after the 180°(inverting)-pulse, with more negative values rendered increasingly darker. Background air is generally rendered a middle shade of gray, not black. Short T1 tissues are always brighter than long T1 tissues, but both can be darker than air at short TI’s. Common applications are in pediatric and cardiac imaging."}}
{"id": "q_SEIR_10", "question": "Concerning the null point value (TInull) for a given tissue in magnitude-reconstructed IR, which statement is false?", "golden_answers": [2], "choices": ["TInull increases with increasing field strength.", "TInull increases with increasing T1 value", "For long TR, TInull ≈  0.69 x T2.", "TInull depends on whether the signal is generated by a conventional spin-echo or fast spin-echo sequence."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 3.0, "hint": "For TR>>T1, TInull = T1 • (ln 2) ≈ 0.69 x T1, (not 0.69 x T2, so answer c is false). Because tissue T1 increases with field strength, TInull does also. TInull depends on echo time of the last echo in a FSE sequence."}}
{"id": "q_SEIR_11", "question": "Which of the following statements about the Short TI Inversion Recovery (STIR) sequence is false?", "golden_answers": [1], "choices": ["It is a very useful technique for fat saturation.", "It is a very useful technique for detecting gadolinium enhancement.", "It has additive T1 and T2 effects.", "It is especially useful in lower field permanent magnets with relatively poor homogeneity."], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "STIR cannot be used as a fat suppression technique post-gadolinium. STIR does not specifically suppress fat; it only suppresses tissues with T1 values in the range of fat (200-300 ms), so gadolinium enhancement would be suppressed."}}
{"id": "q_SEIR_12", "question": "Which of the following pulse sequence parameters might be used to create a T1-FLAIR brain image?", "golden_answers": [0], "choices": ["TR = 2500, TE = 10, TI = 900", "TR = 2500, TE = 50, TI = 180", "TR = 4000, TE = 80, TI = 1800", "TR = 8000, TE = 100, TI = 2500"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "Answer (a) is correct. Answer (b) would be considered a STIR image, while (c) and (d) would be T2-FLAIR images."}}
{"id": "q_SEIR_13", "question": "Double Inversion Recovery (DIR) sequences for brain imaging utilize two different TI values, which typically suppress", "golden_answers": [1], "choices": ["Fat and CSF", "CSF and white matter", "CSF and gray matter", "Gray matter and white matter"], "metadata": {"subject": "Pulse Sequences Quiz", "level": 2.0, "hint": "DIR brain imaging is particularly useful for detecting lesions of the white matter and cortex. Typically the first 180°-pulse suppresses CSF and the second suppresses white matter."}}
{"id": "q_1_00", "question": "Concerning nuclear spin (I), which of the following is true?", "golden_answers": [2], "choices": ["Spin is due to rotation of the nucleus about its axis.", "Protons have spin, but neutrons do not.", "Spin can only have integer or half-integer values.", "Another name for spin is \"precession\"."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Spin is a fundamental quantum property of subatomic particles and does not result from their physical rotation. Many subatomic particles besides the proton have spin, including the neutrons and electrons. Spin is quantized and can take on a limited number of discrete values, so c) is true. When placed in an external magnetic field, nuclear spin results in precession, but spin and precession are not the same."}}
{"id": "q_1_01", "question": "Which of the following spins (I) could a nucleus not possess?", "golden_answers": [2], "choices": ["0", "45293", "45355", "45537"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 4.0, "hint": "Quantum mechanics restricts nuclear spin to only integer or half-integer (1/2, 3/2, 5/2, etc) values, so I = 3/4 is not permitted.  Link to Q&A discussion"}}
{"id": "q_1_02", "question": "Concerning nuclear spin (I), which of the following statements is false?", "golden_answers": [3], "choices": ["A longer but equivalent name for \"spin\" is \"spin angular momentum\".", "For hydrogen (¹H) MRI it is common and acceptable to use the terms \"nucleus\", \"spin\", and \"proton\" interchangeably.", "Routine clinical MRI measures signal from hydrogen (¹H) nuclei only.", "The hydrogen (¹H) nucleus contains one proton and one electron."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The hydrogen (¹H) nucleus contains only a single proton surrounded by an electron cloud, so d) is false. The other statements are all true."}}
{"id": "q_1_03", "question": "Concerning nuclear spin (I), which of the following statements is false?", "golden_answers": [1], "choices": ["Protons and neutrons each have spin = ½.", "To determine net nuclear spin (I), you simply add up the number of protons and neutrons and divide by 2.", "Different isotopes of the same element commonly have different nuclear spins.", "Every element has at least one isotope with non-zero spin."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Net nuclear spin (I) does depend on the total number of protons and neutrons, but no simple formula for I exists as interactions between more elementary components (quarks and gluons) must be considered. The other statements — a), c) and d) — are all true."}}
{"id": "q_1_04", "question": "Concerning nuclear spin (I) and NMR, which of the following statements is false?", "golden_answers": [3], "choices": ["All nuclei can undergo NMR except those containing even numbers of both protons and neutrons.", "Every element in the periodic table has at least one isotope that can undergo NMR.", "Across the periodic table nuclear spins (I) with values ranging from 0 to 8 can be found.", "Nuclei with I = 0 readily undergo NMR."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Only nuclei with non-zero spins can undergo NMR, so d) is false. The other statements are all true."}}
{"id": "q_1_05", "question": "Which of the following statements concerning the magnetic dipole moment is false?", "golden_answers": [3], "choices": ["It is a representation of the nucleus modeled as a tiny bar magnet with north and south poles.", "An alternative representation is a vector (μ) arising from a small current loop.", "Like a compass needle, a dipole moment will tend to align with an externally applied magnetic field to assume its lowest energy state.", "The dipole moment will precess when placed in an external magnetic field."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "The magnetic dipole moment (μ) will experience a torque causing it to align with an externally applied magnetic field, but will not precess around the field."}}
{"id": "q_1_06", "question": "Which of the following statements about a magnetic dipole placed in an external magnetic field is false?", "golden_answers": [0], "choices": ["The dipole is at its lowest energy state when pointing in a direction opposite the field.", "The torque (twisting force) experienced by the dipole is directly proportional to the strength of the external field.", "The torque (twisting force) experienced by the dipole depends on the angle between the dipole and the external field.", "The energy of the dipole-external field system depends on the angle between the dipole and the external field."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The dipole (μ) experiences a torque (τ) given by the vector cross-product τ =  μ x B0. In terms of scalar magnitudes: ||τ|| = ||μ||  ||B0|| sin θ, where θ is the angle between them. The energy (E) is defined by the dot product, E =  −μ • B0 =  −||μ||  ||B0|| cos θ. The energy is at its maximum (not a minimum), when the dipole points opposite the field (θ = 180°), so answer a) is false, ."}}
{"id": "q_1_07", "question": "The dipole magnetic moment (μ) is directly proportional to nuclear spin (I), connected by a constant called the", "golden_answers": [0], "choices": ["Gyromagnetic ratio (γ)", "Planck's constant (h)", "Nuclear susceptibility (χ)", "Chemical shift (δ)"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The two are connected by the gyromagnetic ratio (γ), described through the relationship: μ = γI"}}
{"id": "q_1_08", "question": "Which of the following statements about the gyromagnetic ratio (γ) is false?", "golden_answers": [3], "choices": ["It can be expressed in units of MHz/Tesla.", "It may have a negative value.", "It is different for each element.", "It is the same for all isotopes of a given element."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "The gyromagnetic ratio (γ) is a constant of proportionality between the dipole magnetic moment (μ) and nuclear spin (I). It is commonly expressed in units of MHz/T. Although usually a positive number, it may be negative. A negative value for γ means that the magnetic moment and spin point in opposite directions. The gyromagnetic ratio (γ) is different for every isotope of every element, so answer d) is false."}}
{"id": "q_1_09", "question": "The ¹H nucleus has a spin (I) = ½. When placed in an external magnetic field, its number of measurable spin states (eigenstates) will be", "golden_answers": [3], "choices": ["0", "½", "1", "2"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 4.0, "hint": "The number of observable spin states for a nucleus with spin I equals 2I +1. So the ¹H nucleus has 2(½) + 1 = 2 possible spin states."}}
{"id": "q_1_10", "question": "Besides ¹H, two nuclei commonly studied by NMR spectroscopy are ³¹P and ¹³C. The fact that all three isotopes have identical nuclear spins (I) = ½ means that when placed in an external magnetic field", "golden_answers": [1], "choices": ["They will have exactly the same resonant frequencies.", "They will each exhibit two discrete measurable energy states.", "The difference in energy states will be the same for each isotope.", "They will have the same gyromagnetic ratio (γ)."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "All spin-½ particles will exhibit two discrete energy states when placed in an external magnetic field, so answer b) is true. The isotopes will have different gyromagnetic ratios (γ), different resonant frequencies, and different energy levels, however."}}
{"id": "q_1_11", "question": "²³Na is another NMR active isotope used for imaging research. It has a nuclear spin (I) = 3/2. Compared to the ¹H nucleus with I = 1/2, in an external magnetic field", "golden_answers": [3], "choices": ["²³Na will have a higher gyromagnetic ratio (γ) than ¹H.", "²³Na will have a higher resonance frequency than ¹H.", "²³Na will manifest 3 discrete energy states.", "²³Na will manifest 4 discrete energy states."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "The number of observable energy states for a nucleus with spin I equals 2I +1. The ²³Na nucleus therefore has 2(3/2) + 1 = 4 possible spin states, so answer d) is correct. The gyromagnetic ratio (γ) and hence resonance frequency do not depend on I."}}
{"id": "q_1_12", "question": "The famous experiment demonstrating how spin-½ particles can be physically separated into two groups by a magnetic field was performed in 1922 by", "golden_answers": [2], "choices": ["Einstein", "Heisenberg", "Stern and Gerlach", "Planck and Dirac"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "This is a description of the Stern-Gerlach experiment, often provided as tangible proof for the quantization of nuclear angular momentum visible in the macroscopic world."}}
{"id": "q_1_13", "question": "Which of the following names refers to the highest energy spin state of an ¹H nucleus in a magnetic field?", "golden_answers": [1], "choices": ["Spin-up", "Spin-down", "Parallel", "|+½>"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 1.0, "hint": "The highest energy state occurs when the spin has a direction opposite that of the main magnetic field and is denoted spin-down (correct answer), anti-parallel, or  |−½>."}}
{"id": "q_1_14", "question": "Why don't all the nuclear spins simply fall to their lowest energy states to minimize total system energy?", "golden_answers": [2], "choices": ["They actually do. The above statement is false.", "Such a highly skewed distribution of energy states is prohibited by quantum mechanics.", "Thermal molecular collisions tend to equalize the distribution of nuclei between lower- and higher-energy states.", "The distribution of energy states cannot be known due to the Heisenberg Uncertainty Principle."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "The natural tendency for spins to fall to lower energy states is offset by thermal collisions that tend to equalize the two energy levels. The result is a compromise predicted by the Boltzmann distribution."}}
{"id": "q_1_15", "question": "According to quantum mechanical (QM) theory and experiment, which statement is true?", "golden_answers": [2], "choices": ["A spin-½ particle like the proton must exist exclusively in either the spin-up or spin-down state.", "Conclusive evidence for the QM restriction described in part a) is provided by the Stern-Gerlach experiment.", "Scientists have been able to trap and manipulate spins in a superposition between their up- and down-states.", "There is nearly universal agreement among scientists that the Copenhagen Interpretation of QM is correct."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Quantum mechanics does not require a proton to exist exclusively in one of its two primary (eigen)states, only a linear combination of the two. Thus answer a) is false. The Stern Gerlach experiment only shows that when a measurement is made a group of spin-½ particles that one of two results becomes physically manifest. This does not speak to the underlying quantum reality prior to measurement, however, so b) is also false.  Haroche and Weinland, working independently, were awarded the Nobel Prize for Physics in 2012 for their experiments trapping and manipulating spins in superposition states, so c) is true.  The Copenhagen Interpretation of QM, while still the most popular, is far from being universally accepted, so d) is false. Recent polls of quantum physicists found the Many Worlds Interpretation gaining significant ground.  Of course, neither may be correct!"}}
{"id": "q_2_00", "question": "Nuclear precession can be considered the result of a \"twisting force\" or torque (τ) on a spin's angular momentum as it interacts with an externally applied magnetic field. The orientation of this torque is", "golden_answers": [3], "choices": ["Collinear with the spin.", "Collinear with the spin but in the opposite direction.", "Collinear with the magnetic field.", "Perpendicular to both the spin and magnetic field."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "The torque (τ) is perpendicular to both the spin angular momentum and the magnetic field. This creates a \"twisting force\" that can be thought of as \"pushing the spin from the side\" resulting in nuclear precession rather than alignment with the field. Link to Q&A discussion"}}
{"id": "q_2_01", "question": "Precession may be expressed in either angular (ω0) or cyclic (f0) frequency. The two are are related by the equation", "golden_answers": [0], "choices": ["ω0 = 2 π f0", "f0 = 2 π ω0", "ω0 =  π f0", "f0 = π ω0"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 4.0, "hint": "The correct equation is a). Angular frequency (ω0) is measured in radians per second, where 2 π radians/sec = 360°/sec = 1 cycle (or revolution) per second = 1 Hertz (Hz). Thus the cyclic frequency (f0) must be multiplied by 2 π  to obtain angular frequency (ω0)."}}
{"id": "q_2_02", "question": "The conventional units for angular frequency (ω0) are", "golden_answers": [2], "choices": ["Cycles per second (cps)", "Hertz (Hz)", "Radians/sec", "Revolutions per minute (rpm)"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 4.0, "hint": "The correct answer is c), radians per second. The other options are used to express cyclic frequency (f0)."}}
{"id": "q_2_03", "question": "Which of the following is the correct form of the Larmor equation?", "golden_answers": [0], "choices": ["f0 =  γ B0", "f0 =  γ / B0", "f0 =  B0 /  γ", "None of these equations is correct."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "The correct answer is a), f0 =  γ B0."}}
{"id": "q_2_04", "question": "What is the approximate gyromagnetic ratio (γ) of the ¹H nucleus?", "golden_answers": [1], "choices": ["10.7 MHz/Tesla", "42.6 MHz/Tesla", "64.0 MHz/Tesla", "128 MHz/Tesla"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The correct answer is b), 42.6 MHz/Tesla. I don't think you need to memorize this number, but it can easily be retrieved as I do believe everyone involved with MRI should know that a 1.5T scanner has a resonance frequency of about 64 MHz. Thus γ ≈ 64 MHz ÷ 1.5 Tesla, giving a γ of about 42.6 MHz/T."}}
{"id": "q_2_05", "question": "If the ¹H resonance frequency in a 1.5T scanner is about 64 MHz, what is the approximate ¹H resonance frequency at 7T?", "golden_answers": [2], "choices": ["128 MHz", "256 MHz", "298 MHz", "426 MHz"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Resonance frequency is directly proportional to field strength. So the ¹H resonant frequency at 7.0T can be calculated as 64 MHz x (7.0/1.5) ≈ 298 MHz.  Link to Q&A discussion"}}
{"id": "q_2_08", "question": "Which of the following statements about nuclear precession is true?", "golden_answers": [2], "choices": ["Nuclear precession will not begin until a radiofrequency pulse is applied.", "Sustaining nuclear precession requires the continual input of energy from the environment.", "Protons in every drop of water in the ocean and in every snowflake at the north pole are precessing right now.", "It is impossible to obtain MR images using the earth's magnetic field because it is so small."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Nuclear precession occurs spontaneously when protons are placed in any magnetic field.  No energy input is required to start or sustain precession. Precession occurs even in the tiniest magnetic fields, including that of the earth, so answer c) is true. In fact, crude MR images using the earth's magnetic field alone have been obtained."}}
{"id": "q_2_09", "question": "The slight difference in resonant frequencies noted between ¹H-nuclei in different molecular environments is due to", "golden_answers": [1], "choices": ["Different gyromagnetic ratios", "Different local magnetic fields", "Different relaxation times", "Different spin quantum numbers"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "This question concerns the origin of chemical shift. Variable shielding and deshielding of ¹H-nuclei by molecular electron clouds results in slightly different local magnetic fields that each nucleus experiences. These different local fields alter resonance frequencies slightly.   Link to Q&A discussion"}}
{"id": "q_2_10", "question": "Chemical shifts (δ) are typically reported in units of", "golden_answers": [2], "choices": ["Gauss (G)", "Millitesla per meter (mT/m)", "Parts per million (ppm)", "Percent (%)"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Chemical shifts are typically reported in ppm, which is independent of field strength. Note that ppm, like %, is dimensionless.  Link to Q&A discussion"}}
{"id": "q_2_11", "question": "The abbreviation \"ppm\" stands for", "golden_answers": [3], "choices": ["Proton paramagnetic moment", "Proton-proton magnetization", "Precession per minute", "Parts per million"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The correct answer is d), \"parts per million\", the commonly used field-independent method to report chemical shifts."}}
{"id": "q_2_12", "question": "The chemical shift (δ) between water and fat protons measured at 1.5T is approximately 3.5 ppm. What would their chemical shift be at 3.0T?", "golden_answers": [1], "choices": ["1.75 ppm", "3.5 ppm", "7.0 ppm", "10.5 ppm"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The chemical shift (δ) in ppm is independent of field strength, so b) is correct."}}
{"id": "q_2_14", "question": "At 1.5 T the chemical shift between water and fat protons results in a frequency difference of approximately 220 Hz. What would be their frequency difference at 3.0T?", "golden_answers": [2], "choices": ["110 Hz", "220 Hz", "440 Hz", "660 Hz"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Field strength is doubled, so Larmor frequency is doubled, and frequency difference due to chemical shift is also doubled. The correct answer is therefore c)."}}
{"id": "q_2_15", "question": "Which of the following statements concerning the net magnetization (M) is false?", "golden_answers": [3], "choices": ["M can be considered the vector sum or average millions of individual nuclear spins.", "Using M allows the NMR phenomenon to be analyzed using classical (rather than quantum) physics.", "At equilibrium, M is aligned with the external magnetic field.", "At equilibrium, M precesses around the direction of the external magnetic field."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "All statements are true except d). At equilibrium, M is stationary and aligned with the external magnetic field. Application of an RF-pulse is required to tip M out of alignment with B0 at which time it will begin to precess."}}
{"id": "q_2_16", "question": "In an unmagnetized sample of material far away from strong external magnetic fields, the net magnetization (M)", "golden_answers": [0], "choices": ["Is effectively zero in all directions.", "Has a significant non-zero longitudinal component.", "Has significant non-zero transverse components.", "Spontaneously precesses."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "In the absence of a strong external magnetic field, individual proton spins are randomly oriented in space and their vector sum is essentially zero in all directions. In reality, however, some small external magnetic field is always present, if only from the earth itself. Thus M is only effectively (but never completely zero) in all directions."}}
{"id": "q_2_17", "question": "Why does the net magnetization (M) of an unmagnetized sample of material placed in a magnetic field not initially develop transverse components?", "golden_answers": [3], "choices": ["This premise of the question is false; M develops transverse components from the very beginning.", "The transverse components are not seen at first because they take several seconds to develop.", "The transverse components are neutralized by the precession of M.", "The individual spins contributing to M have randomly dispersed transverse components lacking phase coherence."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Answer d) is correct because the spins have random transverse components of angular momentum. An RF-pulse or energy input near the Larmor frequency will be necessary to generate some phase coherence and transverse components.  Link to Q&A discussion"}}
{"id": "q_2_18", "question": "What intrinsic tissue parameter determines the rate at which the longitudinal component of the net magnetization (M) initially develops?", "golden_answers": [1], "choices": ["Spin density (ρ)", "T1", "T2", "T2*"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 1.0, "hint": "The initial growth of longitudinal magnetization (Mz) is a simple exponential with time constant T1."}}
{"id": "q_2_19", "question": "Which of the following statements concerning net magnetization (M) is false?", "golden_answers": [3], "choices": ["Net magnetization (M) develops when an unmagnetized sample of tissue is placed in an external magnetic field.", "Initially M grows in the longitudinal direction as the individual spins seek to align with B0.", "When tipped out of alignment with B0, M will precess at the same resonance frequency as the individual nuclei comprising it.", "M will continue to precess even when completely inverted and pointing in the −z direction (i.e. opposite to B0)."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Only d) is false. Even though the individual spins comprising M are always precessing, M itself does not precess unless tipped out of alignment with B0 allowing it to develop nonzero transverse components. Once M is completely inverted 180° with respect to B0, it no longer has transverse components and is no longer precessing. If left alone after such an inversion, M will simply regrow along the z-axis to return to its initial orientation and magnitude aligned with B0."}}
{"id": "q_2_20", "question": "Which of the following statements about nuclear magnetic resonance is false?", "golden_answers": [3], "choices": ["Tipping the net magnetization (M) out of initial alignment with B0 requires absorption of energy by the spin system.", "In MRI, the source of energy required to initiated NMR is typically provided by a rotating/oscillating radiofrequency field named B1.", "This tipping of (M) is a manifestation of the NMR phenomenon.", "Nuclear precession and resonance are essentially the same."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "All statements are true except d). Nuclear precession is experienced by all non-zero spin particles when placed in an external magnetic field and requires no input of energy. NMR is a special condition of a spin system requiring the absorption and release of energy over a narrow range of frequencies."}}
{"id": "q_3_00", "question": "Which of scientist first experimentally demonstrated the NMR phenomenon in the 1930's and gave it its name?", "golden_answers": [1], "choices": ["Felix Bloch", "Isidor Rabi", "Edward Purcell", "Peter Mansfield"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Isidor Rabi is credited with naming NMR and being the first to demonstrate its existence experimentally in a molecular beam of LiCl."}}
{"id": "q_3_01", "question": "Which of the following statements about the NMR discoveries of Felix Bloch and Edward Purcell is true?", "golden_answers": [2], "choices": ["The two worked together in adjacent labs at Harvard.", "Their experimental setups were nearly identical.", "Their initial reports were published simultaneously in 1946.", "Only Bloch received the Nobel Prize for his research."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Bloch performed his research at Stanford at the same time Purcell was working independently at MIT. Their experimental setups were quite different, Bloch detecting an induction signal from water and Purcell measuring energy absorption in solid paraffin wax. Their initial reports were published simultaneously in the January, 1946 issue of the journal Physical Review, so answer c) is true. Bloch and Purcell jointly received the Nobel Prize for Physics in 1952."}}
{"id": "q_3_02", "question": "The radiofrequency (RF) field used to inject energy into a spin system to induce nuclear resonance is called", "golden_answers": [1], "choices": ["B0", "B1", "B2", "Mxy"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The correct answer is B1. B0 is the main magnetic field and Mxy are the transverse components of net magnetization induced by B1. There is no field called B2."}}
{"id": "q_3_06", "question": "(Advanced) Which of the following statements concerning the spin-system immediately after a 90°-pulse is true?", "golden_answers": [0], "choices": ["If the z-component of angular momentum were measured for all protons, an equal number of spin-up and spin-down states would be observed.", "The 90°-pulse causes the spins to precess around B1.", "The spins all become locked into phase coherence with one another.", "The spin angular momentum for each proton is turned so that it points horizontally in the direction of B1."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "This is a pretty tricky question that really probes one's understanding of the NMR phenomenon. Only a) is true. If the longitudinal angular momentum of all spins were measured (by passing them through all Stern-Gerlach device, for example), an equal distribution of spin-up and spin-down states would be observed. Remember that spins do not exist in pure eigenstates, so it is not correct to say there are an equal number of spin-up and spin-down protons (though that statement is commonly found in textbooks). But the idea is much the same. Option b) is false, but only barely so. Precession after a 90°-pulse occurs around the direction of B0, just as it did prior to the RF-pulse. During the application of the RF-pulse, however, procession occurs around both B0 and B1, described in more detail in the Q&A's about the rotating frame.  Option c) is false, as no \"magical\" locking together of spins occurs. What we call \"phase coherence\" is simply the same initially skewed longitudinal distribution of spin energies that have been rotated into the transverse plane by the RF-pulse. Finally, option d) is false. By the Heisenberg uncertainty principle we cannot know the direction a spin is \"pointing\", so the statement is meaningless. But I'm pretty sure the spins would not all be \"pointing\" horizontally if we were able to know!"}}
{"id": "q_3_08", "question": "The complex motion of the net magnetization vector (M) when acted upon by both B0 and B1 can be simplified by considering the system in the", "golden_answers": [1], "choices": ["Laboratory frame of reference.", "Rotating frame of reference.", "Earth's frame of reference.", "Adiabatic frame of reference."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 4.0, "hint": "The rotating frame of reference allows the motion of (M) to be simplified by removing the simple Larmor precession around B0. It's like riding on a merry-go-round instead of watching it from stationary ground nearby."}}
{"id": "q_3_09", "question": "(Advanced) What happens if the B1 field is not applied exactly at the Larmor frequency?", "golden_answers": [2], "choices": ["Spins will not be affected and will continue to precess only around B0.", "Spins will stop precessing around B0 and begin to precess around B1.", "Spins will precess around an effective field Beff in the rotating frame that takes into account of off-resonance B1 and B0 effects.", "The spin system will experience random and unpredictable fluctuations in energy levels."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 4.0, "hint": "The correct answer is c). It describes the \"off-resonance\" condition which is commonly encountered in MR imaging where a span of RF-frequencies is transmitted and gradients affect Larmor frequencies across the object being imaged."}}
{"id": "q_3_10", "question": "(Advanced) Which of the following statements about adiabatic excitation is false?", "golden_answers": [3], "choices": ["Unlike \"conventional\" RF-pulses that are purely amplitude-modulated, adiabatic RF-pulses are also frequency-modulated.", "The fat-suppression technique SPAIR uses adiabatic inversion.", "Adiabatic pulses are relatively insensitive to B1 field inhomogeneities.", "Doubling the duration of a 90°-adiabatic pulse creates a 180°-adiabatic pulse."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 4.0, "hint": "All statements are true except d). Unlike \"conventional\" RF-pulses, the flip angle of an adiabatic pulse is NOT proportional to its magnitude and duration. An adiabatic pulse cannot be easily scaled or stretched to change its effect."}}
{"id": "q_4_00", "question": "Which of the following is not a synonym for T1 relaxation?", "golden_answers": [0], "choices": ["Spin-spin relaxation", "Spin-lattice relaxation", "Longitudinal relaxation", "Thermal relaxation"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Spin-spin relaxation is a synonym for T2 relaxation."}}
{"id": "q_4_01", "question": "Which of the following is/are synonyms for T2 relaxation?", "golden_answers": [3], "choices": ["Spin-spin relaxation", "Transverse relaxation", "Thermal relaxation", "Both a) and b)"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Thermal relaxation is a synonym for T1."}}
{"id": "q_4_02", "question": "Which of the following statements about T1 relaxation is false?", "golden_answers": [3], "choices": ["T1 is the time constant for regrowth of longitudinal magnetization (Mz).", "T1 relaxation requires an energy transfer between spins and their environment (\"lattice\").", "T1 relaxation results in a net energy loss from the spin system.", "This energy loss occurs by spontaneous emission of photons from the protons."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "All are true except d). T1 relaxation requires release of absorbed energy from the spin system to the external environment, but this such energy transfer must be stimulated by interaction with a fluctuating field near the Larmor frequency arising from a nearby proton or molecule."}}
{"id": "q_4_03", "question": "When an unmagnetized sample is placed in a magnetic field, an internal magnetization (M) will develop and grow to a maximum value in the longitudinal direction (M0). The first order exponential time constant for this growth is defined as", "golden_answers": [0], "choices": ["T1", "T1*", "T2", "T2*"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "This is the definition of T1 as described by Felix Bloch."}}
{"id": "q_4_04", "question": "T1 is the time required for the longitudinal magnetization Mz to grow from zero to about ____ of its maximum value (M0)", "golden_answers": [2], "choices": ["0,37", "0,5", "0,63", "1"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 1.0, "hint": "The equation for exponential regrowth is Mz = M0 (1 − e−t/T1). After one time constant (i.e., at t = T1), Mz will have reached (1 − e−1) or about 63% of its maximum value (M0). Link to Q&A discussion"}}
{"id": "q_4_05", "question": "T2 is the time required for the transverse components of magnetization M0 to decay to approximately ____ from their maximum initial value after a 90°-pulse.", "golden_answers": [0], "choices": ["0,37", "0,5", "0,63", "1"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 1.0, "hint": "The equation for exponential decay of transverse magnetization immediately after a 90°-pulse where the initial magnetization (M0) has been tipped into the transverse plane is given by: Mxy = M0 e−t/T2. After one time constant (i.e., at t = T2), Mxy will have decayed by (e−1) or to about 37% of its initial value."}}
{"id": "q_4_06", "question": "Which of the following statements concerning T2 relaxation is false?", "golden_answers": [0], "choices": ["Any process causing T2 relaxation also results in T1 relaxation.", "A major cause of T2 relaxation is dephasing of spins by static local field inhomogeneities.", "Another major cause of T2 relaxation is spin-spin \"flip-flop\" interactions.", "T2 relaxation may occur with or without energy transfer/loss from the spin system."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Only a) is false, but its converse is true, \"Any process causing T1 relaxation also results in T2 relaxation\". The other options are correct."}}
{"id": "q_4_07", "question": "If the T1 relaxation time for brain tissue is 1000 ms, what is its relaxation rate (R1)?", "golden_answers": [2], "choices": ["1000 msec", "1 sec", "1 sec−1", "1 msec−1"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 4.0, "hint": "Relaxation rate is merely the inverse of relaxation time. So R1 = 1/T1 = 1/1000 msec = 1/(1 sec) = 1 sec−1"}}
{"id": "q_4_09", "question": "Which of the following relaxation time pairs for tissue is impossible?", "golden_answers": [3], "choices": ["T1 = 4000 ms, T2= 2000 ms", "T1 = 1000 ms, T2 = 100 ms", "T1 = 500 ms, T2 = 20 ms", "T1 = 500 ms. T2 = 600 ms"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Because every process that causes T1 relaxation also causes T2 relaxation, but T2 relaxation can occur without T1 relaxation, T2 is always less than or equal to T1. Thus the combination in choice d) is impossible."}}
{"id": "q_4_10", "question": "Which of the following biological materials would be expected to have the shortest T2 values?", "golden_answers": [1], "choices": ["Urine", "Achilles tendon", "Spleen", "Liver"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "T2 relaxation occurs most quickly when local static magnetic fields are present that dephase the spins. The more \"solid\" and \"drier\" the tissue, the shorter is its T2 value. Of the choices above, tendon has the shortest T2."}}
{"id": "q_4_11", "question": "Which of the following biological materials would be expected to have the shortest T1 values?", "golden_answers": [0], "choices": ["Scalp fat", "Pus", "Liver", "Spleen"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Because of their size and shape, triglycerides (the main component of adipose tissue as in scalp fat) have a relatively large fraction of molecular motions near the Larmor frequency, making them efficient at T1 relaxation. So the correct answer is a). Yellow bone marrow has relatively short T1 due to fat deposition, but red marrow has much less fat and is filled with water-containing hematopoietic cells."}}
{"id": "q_4_12", "question": "Which of the following biological materials would be expected to have the longest T2 values?", "golden_answers": [2], "choices": ["Colloid cyst in the thyroid", "Pus", "Urine in the bladder", "Kidney"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Free or \"unbound\" water molecules tumble most rapidly averaging out static dipolar interactions and hence have the longest T2 values. So pure liquids like spinal fluid and urine have the longest T2 values."}}
{"id": "q_4_13", "question": "Which of the following statements about T2* is false?", "golden_answers": [0], "choices": ["T2* is always longer than T2.", "T2 is always longer than T2*.", "T2* includes not only \"true\" T2 effects but also effects of magnetic field inhomogeneities.", "T2* includes not only \"true\" T2 effects but also effects of magnetic field inhomogeneities."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "T2* includes not only \"true\" T2 effects but also effects of magnetic field inhomogeneities."}}
{"id": "q_4_14", "question": "Which of the following molecular mechanisms is the most important for causing T1 and T2 relaxation in ¹H NMR?", "golden_answers": [0], "choices": ["Dipole-dipole interactions", "Chemical shift anisotropy", "Chemical shift anisotropy", "Molecular translation/diffusion"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "All these mechanisms make contributions, but the dipole-dipole interaction is the most important. Dipole-dipole interactions are \"through space\" magnetic field disturbances typically occurring between nuclear or electron spins on the same or closely apposed molecules."}}
{"id": "q_4_17", "question": "In dipole-dipole interactions, T1 relaxation is most efficient (and T1 values are shortest) for", "golden_answers": [1], "choices": ["Small, rapidly tumbling molecules", "Molecules tumbling near the Larmor frequency", "Large, slowly moving molecules", "Macromolecules bound to a rigid biologic scaffold or matrix"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Since T1 relaxation requires stimulated energy exchange at the Larmor frequency, spins on molecules tumbling at near the Larmor frequency are most efficient at T1 relaxation."}}
{"id": "q_4_18", "question": "In dipole-dipole interactions, T2 relaxation is most efficient (and T2 values are shortest) for", "golden_answers": [3], "choices": ["Small, rapidly tumbling molecules.", "Molecules tumbling near the Larmor frequency.", "Large, slowly moving molecules.", "Macromolecules bound to a rigid biologic scaffold or matrix"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Stationary local magnetic fields are most effective at inducing T2 relaxation, so nearly immobile macromolecules (especially those bound to bones, cell membrane, or collagen) have the shortest relaxation times of all. Small, rapidly tumbling molecules have very long T2 values."}}
{"id": "q_4_19", "question": "Considering the effects of macromolecules on relaxation times, which of the following is false", "golden_answers": [2], "choices": ["Macromolecules themselves often have extremely short T2 values and their signal may decay too quickly to be detected using conventional MRI techniques.", "A \"bound\" or \"hydration\" layer of water molecules with restricted motion is generally found adjacent to macromolecules.", "These \"bound\" water protons interact exclusively with macromolecules and not with the \"free water\" pool.", "Bound water molecules tumble more slowly, producing shortening of T1 and T2. This partially explains the reduced T1 and T2 values of tissues compared to free water."], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Only c) is false. The bound water molecules interact and exchange magnetization both with the macromolecules and the free water pool."}}
{"id": "q_4_20", "question": "Which of the following ¹H-containing molecules account for nearly 100% of the signal recorded within the brain parenchyma using routine MRI sequences?", "golden_answers": [0], "choices": ["Water", "Triglycerides", "Myelin", "N-acetyl aspartate (NAA)"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Triglcerides are present in scalp fat, but not in the brain parenchyma itself. Myelin is  present in the brain, but as an immobile macromolecule has an extremely short T2 and whose signal thus decays too rapidly to be detected using conventional MRI sequences. NAA is the brain metabolite with the largest peak seen on MR spectroscopy of the brain, but its concentration is many thousand times lower than that of water."}}
{"id": "q_4_21", "question": "By irradiating tissue with an off-resonance RF-pulse it is possible to affect image contrast by transferring energy between macromolecular and free-water pools. This process is known as", "golden_answers": [1], "choices": ["T1 exchange", "Magnetization transfer", "Chemical shift", "Energy swap"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "This is a brief description of MT.  Link to Q&A discussion"}}
{"id": "q_4_22", "question": "As field strength increases from 0.5T to 3.0T, the T1 of most tissues", "golden_answers": [0], "choices": ["Increases", "Decreases", "Remains about the same", "Decreases then increases"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "For most biological tissues, empirical measurements suggest that T1 increases approximately as B0⅓. Therefore, measured T1 values of most tissues will approximately double as field strength is raised from 0.3 T to 3.0 T."}}
{"id": "q_4_23", "question": "As field strength increase from 0.5T to 3.0T, the T2 of most tissues", "golden_answers": [2], "choices": ["Increases", "Decreases", "Remains about the same", "Decreases then increases"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The effect varies depending on tissue type, but generally there is relatively little change in T2 values over the 0.5T to 3.0T range. T2 definitely shortens for fields > 3.0T, however."}}
{"id": "q_RELAXCLIN_00", "question": "The MR signal in adipose tissue comes primarily from hydrogen protons in", "golden_answers": [1], "choices": ["Free fatty acids", "Long-chain triglycerides", "Short-chain triglycerides", "Cholesterol"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "The major MR signal in adipose tissue comes from long-chain aliphatic triglycerides, 16-20 carbon atoms in length, that are mostly saturated (−(CH2)n−)."}}
{"id": "q_RELAXCLIN_01", "question": "Protons in which lipid elements do not contribute significantly to the bright MR signal of fat on routine T1-weighted imaging?", "golden_answers": [0], "choices": ["Cell membrane phospholipids", "Liquid forms of cholesterol", "Free fatty acids", "Triglyceride methyl groups"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "Phospholipids and sphingolipids, present in cell membranes and myelin respectively, have exceedingly short T2 values and their MR signal is not directly recorded using routine MR sequences. They can be recorded using ultrashort TE (UTE) methods."}}
{"id": "q_RELAXCLIN_02", "question": "Examples of bright T1 signal due to exogenous lipids include all of the following except", "golden_answers": [1], "choices": ["Intrathecal Pantopaque™ from myelography in the 1980s", "A commercial MR skin marker", "A vitamin E capsule skin marker", "Vaseline (petroleum jelly) on the skin"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "Although vitamin E capsules, fish oil capsules, and bath oil beads may be used as skin markers in MRI, they cannot be seen on fat-suppressed images. Commercial MR skin markers contain a dilute paramagnetic solution visible on all pulse sequences. Link to Q&A discussion"}}
{"id": "q_RELAXCLIN_04", "question": "Why do areas of microcalcification sometimes appear bright on T1-weighted images?", "golden_answers": [2], "choices": ["The calcium nucleus also undergoes NMR and mixes with the ¹H signal", "You are seeing a susceptibility artifact, not a true change in relaxation time", "Interaction with salts on porous calcium surfaces slows rotation of water molecules", "Microcalcifications often have fat-containing bone marrow within them"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 3.0, "hint": "The high signal is not coming from the calcium itself, as Ca is an even-numbered element with zero spin and no intrinsic MR signal.  The signal is coming from water protons, whose molecular rotation rates have been slowed to near the Larmor frequency by surface interactions with the calcium salts.  This rotational slowing results in short T1 and hence brightness on T1-weighted images."}}
{"id": "q_RELAXCLIN_05", "question": "The T1-bright signal of meconium is primarily due to", "golden_answers": [0], "choices": ["Paramagnetic minerals", "Free fatty acids", "Carbohydrates", "Mucin"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 4.0, "hint": "Although several physical properties contribute to the relaxation times of meconium, the dominant process is likely the accumulation of paramagnetic (Fe, Mn, Mg) minerals within it.  Meconium also contains free fatty acids, carbohydrates, and mucin, but their effects on T1 relaxation are thought to be minor."}}
{"id": "q_RELAXCLIN_06", "question": "The “magic angle” effect takes place when two magnetic dipoles form an angle of about how many degrees with each other?", "golden_answers": [2], "choices": ["30º", "45º", "55º", "60º"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The dipolar interaction due to the static field vanishes at the magic angle of approximately 54.7º."}}
{"id": "q_RELAXCLIN_07", "question": "Interaction of two dipoles at the magic angle affects", "golden_answers": [1], "choices": ["T1 only", "T2 only", "T1 and T2", "Neither T1 nor T2"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The magic angle effect lengthens T2 with theoretically no effect on T1."}}
{"id": "q_RELAXCLIN_08", "question": "Which tissue in the list below does not normally demonstrate signal changes on MRI due to the magic angle effect?", "golden_answers": [0], "choices": ["Liver", "Tendon", "Cartilage", "Peripheral nerve"], "metadata": {"subject": "The NMR Phenomenon Quiz", "level": 2.0, "hint": "The magic angle effect is important in the clinical MR imaging of certain tissues that are highly structured and are oriented obliquely to the main magnetic field (especially tendons, cartilage, and peripheral nerves). The MR signal may spuriously increase near the magic angle mimicking pathology. Liver has no single direction anatomic structure and would not display a magic angle effect."}}