Cardiovascular and MRA Quiz

Cardiovascular and MRA Quiz

Flow Effects in MRI

  1. Bulk blood flow (Q) through a certain point in the vascular tree within a given period of time is measured in what units?
    1. cm/s
    2. cm/s²
    3. cm²/s
    4. cm³/s

    Bulk flow is a volume per unit time and is expressed in units of cm³/s. Link to Q&A discussion

  2. What is the approximate bulk blood flow (Q) passing through a 2 cm diameter artery where the average velocity is 50 cm/s?
    1. 25 cm³/s
    2. 50 cm³/s
    3. 100 cm³/s
    4. 160 cm³/s

    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. Link to Q&A discussion

  3. In what part of a vessel is the blood flow the slowest?
    1. Adjacent to the wall of the vessel
    2. In the center of the vessel
    3. Half-way between the wall and center
    4. The blood flow is the same across the entire vessel.

    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. Link to Q&A discussion

  4. Which blood vessel normally demonstrates a prominent reversal of flow during the cardiac cycle?
    1. Vertebral artery
    2. Ascending thoracic aorta
    3. Middle cerebral artery
    4. Renal artery

    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. Link to Q&A discussion

  5. Which blood vessel has the greatest peak velocity?
    1. Thoracic aorta
    2. Abdominal aorta
    3. Carotid artery
    4. Renal artery

    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. Link to Q&A discussion

  6. What happens to peak velocities as a vessel goes becomes increasingly stenotic?
    1. They decrease.
    2. They increase.
    3. They remain the same.
    4. They increase initially then decrease.

    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. Link to Q&A discussion

  7. In ideal laminar flow the distribution of velocities in cross-section across a vessel should be
    1. Linear
    2. Constant
    3. Parabolic
    4. Hyperbolic

    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. Link to Q&A discussion

  8. In which anatomic situation would you not expect to find vortex flow?
    1. Distal to a carotid artery stenosis
    2. In the proximal (ascending) aorta
    3. In the distal thoracic aorta
    4. In an abdominal aortic aneurysm

    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). Link to Q&A discussion

  9. Which statement about the Reynolds number (Re) in ideal fluids is true?
    1. Values of Re < 2000 predict turbulent flow.
    2. Values of Re > 2500 predict laminar flow.
    3. Re is a velocity with units of cm/sec.
    4. Re is a dimensionless parameter.

    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. Link to Q&A discussion

  10. In which situation would you be more likely to see turbulent flow?
    1. In a vessel with a small diameter
    2. In a vessel with rapid blood velocities
    3. In a vessel with elevated blood viscosity
    4. In the stump of a newly occluded vessel

    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. Link to Q&A discussion

  11. Which one of the following flow-related phenomena is considered a time-of-flight (TOF) effect?
    1. High intravascular signal in an entry slice.
    2. Signal loss due to in-plane flow within an imaging gradient.
    3. Signal loss due to turbulent flow in an aneurysm.
    4. High signal in a vessel due to gradient moment nulling.

    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. Link to Q&A discussion

  12. TEXTFORquestion12
    1. Increase in flowing spin phases as they pass into an imaged slab.
    2. Partial saturation of the imaged slab by repetitive short TR pulses.
    3. Hyperpolarization of inflowing spins.
    4. Combined effect of 90° and 180° pulses on the flowing spins

    The correct answer is (b). "Fresh" blood flowing into the imaged slab has not been subjected to these RF-pulses and is therefore fully magnetized (unsaturated, but not hyperpolarized). When a bolus of this fresh blood enters a slice and is subjected to its first set of RF-pulses, its signal is significantly stronger than that of the tissues (and other blood) within the slab. Link to Q&A discussion

  13. Which statement concerning high-velocity signal loss (“washout”) is incorrect?
    1. High-velocity signal loss is considered a time-of-flight effect.
    2. It is typically seen in arteries and larger veins flowing perpendicular to the plane of imaging.
    3. It is seen primarily in gradient echo imaging sequences.
    4. It can occur anywhere in the imaging slab and is not confined to the end slices.

    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. Link to Q&A discussion

  14. 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
    1. t
    2. t²
    3. v²
    4. G²

    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. Link to Q&A discussion

  15. 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?
    1. No blood flow is present in the basilar artery.
    2. Some flow in the basilar artery may be present, but it is very weak.
    3. The basilar artery contains flowing blood.
    4. A thrombus is present in the basilar artery.

    “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. Link to Q&A discussion

  16. Which of the following statements is not a reason gradient echo sequences can be used to preserve or accentuate signal from flowing blood?
    1. Gradient refocusing of spins is slice-selective.
    2. Relatively short echo times possible with GRE minimize T2* dephasing.
    3. Sequential mode acquisition with GRE makes every slice an “entry slice” with flow-related enhancement.
    4. Moderate-to-large flip angles with GRE saturate stationary tissue and accentuate T2/T1 contrast of blood.

    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. Link to Q&A discussion

  17. Which of the following is not a limitation of the flow compensation (gradient-moment nulling) technique?
    1. Increased minimum TE
    2. Increased energy deposition (SAR)
    3. Inability to correct for nonconstant velocities or acceleration
    4. Increased stress on gradients

    All are true except (b). No extra RF pulses are used, just additional gradient lobes, so no additional energy is deposited by GMN. Link to Q&A discussion

  18. In which situation would refocused misregistered flow signal most likely to be observed?
    1. In a vessel running parallel to the phase-encode axis.
    2. In a vessel running perpendicular to the phase-encode axis.
    3. In sequences with very short TE values.
    4. In sequences where flow compensation (gradient-moment nulling) is used.

    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. So (d) is the correct answer. Link to Q&A discussion

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MR Angiography - I

  1. Which of the following methods is considered a “dark blood” MRA technique?
    1. Time-of-flight MRA
    2. Gadolinium-enhanced MRA
    3. SSFP MRA
    4. Susceptibility-weighted MRA

    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. Link to Q&A discussion

  2. Which of the following methods is not a “bright blood” MRA technique?
    1. Phase-contrast MRA
    2. Double inversion recovery MRA
    3. Arterial spin-labeled MRA
    4. Ferumoxytol-enhanced MRA

    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. Link to Q&A discussion

  3. Which of the following is not an advantage of dark-blood compared to bright-blood MRA techniques?
    1. Less overestimation of stenosis
    2. Better delineation of vessel walls
    3. Better sensitivity to low-flow states
    4. Fewer pulsation artifacts

    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. Link to Q&A discussion

  4. What is the purpose of the so-called “traveling sat” pulses in 2D-TOF MRA?
    1. To reduce venous contamination
    2. To maximize contrast between stationary tissues and blood
    3. To minimize signal losses from phase dispersion
    4. To increase signal from inflowing spins

    These sat pulses are used to suppress venous signal that would normally flow into each slice. Link to Q&A discussion

  5. What is the purpose of using moderate-to-large flip angles (30°−60°) in 2D-TOF-MRA sequences?
    1. To reduce venous contamination
    2. To maximize contrast between stationary tissues and blood
    3. To minimize signal losses from phase dispersion
    4. To increase signal from inflowing spins

    Larger flip angles produce more magnetic saturation of stationary tissues within the imaged volume, and thus maximize contrast with inflowing blood. Link to Q&A discussion

  6. Concerning optimal parameter selection for TOF MRA sequences, which of the following statements is true?
    1. TR should be very long to insure the greatest degree of inflow enhancement.
    2. TE should be very long to increase vascular signal from T2 effects.
    3. Slice orientation should be perpendicular to the direction of flow.
    4. Flip angle (α) should be very small to increase tissue saturation.

    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. Link to Q&A discussion

  7. 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?
    1. 10 ms
    2. 20 ms
    3. 30 ms
    4. 40 ms

    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 Link to Q&A discussion

  8. Concerning magnetization-transfer enhanced MRA, which statement is false?
    1. It is effective for both time-of-flight and phase-contrast MRA
    2. It is effective for both non-contrast and contrast-enhanced MRA
    3. Small vessel detail is improved
    4. Image acquisition time is slightly prolonged.

    MT-MRA is used only for TOF and contrast-enhanced MRA. It offers no benefit for PC-MRA. Link to Q&A discussion

  9. Concerning variable (ramped) pulses, which statement is true?
    1. They are useful in both 2D and 3D TOF MRA.
    2. Their flip angles are designed to decrease linearly along the direction of flow.
    3. They are designed to produce greater saturation of stationary tissues deep in the slab.
    4. They are designed to increase the absolute signal of flowing blood deep in the slab.

    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. Link to Q&A discussion

  10. A common artifact seen with MOTSA MRA is called
    1. The venetian blind artifact
    2. The stair-step artifact
    3. The velocity aliasing artifact
    4. The ringing (Maki) artifact

    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. Link to Q&A discussion

  11. A common artifact seen with 2D-TOF MRA is called
    1. The venetian blind artifact
    2. The stair-step artifact
    3. The velocity aliasing artifact
    4. The ringing (Maki) artifact

    The stair-step artifact is common on 2D-TOF MRA because patient motion between slices. Link to Q&A discussion

  12. 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?
    1. Its appearance will be identical to the contralateral (normally flowing) vertebral artery.
    2. It will appear paradoxically brighter than contralateral vertebral artery.
    3. It will appear slightly less bright than the contralateral vertebral artery.
    4. It will be non-visualized, suggesting an occlusion.

    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. Link to Q&A discussion

  13. Why might a phase-contrast (PC) MRA of the head be preferred over a TOF MRA in a patient with cerebral hemorrhage?
    1. The spatial resolution of PC MRA is much higher.
    2. PC MRA has been shown to be more accurate in the detection of aneurysms.
    3. T1-shine through of a hematoma does not affect PC MRA but may obscure TOF MRA.
    4. The acquisition time of PC MRA is much shorter than equivalent TOF techniques.

    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. Link to Q&A discussion

  14. The underlying mechanism of phase-contrast MRA is based on
    1. Bipolar flow-encoding gradients
    2. Unipolar flow-encoding gradients
    3. RF-phase cycling between excitations
    4. Use of a linear gradient with constant slope along the phase-encoding axis

    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. Link to Q&A discussion

  15. The units of the VENC (velocity-encoding) parameter for PC MRA are
    1. dimensionless
    2. cm/s
    3. cm²/s
    4. cm/s²

    VENC is a velocity, so the correct answer is (b), cm/s. Link to Q&A discussion

  16. 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
    1. +60º
    2. +90º
    3. +180º
    4. +360º

    For a given VENC, the bipolar gradients are adjusted so blood velocities at this level are assigned a +180º phase shift. Link to Q&A discussion

  17. 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?
    1. +50 cm/s
    2. +75 cm/s
    3. +25 cm/s
    4. −25 cm/s

    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! Link to Q&A discussion

  18. 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
    1. 148 cm/s
    2. 92 cm/s
    3. 72 cm/s
    4. 44 cm/s

    By definition, speed = √{v²x + v²y + v²z} = √{(−52)² + (+24)² + (+72)²} = √{8464} = 92 cm/s. Link to Q&A discussion

  19. 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?
    1. Less than 1%
    2. About 5%
    3. 15% - 25%
    4. More than 25%

    The two measurements are generally within about 5% of each other. Link to Q&A discussion

  20. Which of the following situations would velocity measurements by PC MRA be the most accurate?
    1. Imaging plane perpendicular to the direction of flow
    2. Pixel size close to the vessel diameter
    3. Turbulent flow
    4. Sampling of great vessel flows using 8 frames per cardiac cycle.

    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 Link to Q&A discussion

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MR Angiography - II

  1. Which statement about Gated 3D-FSE MRA techniques is incorrect?
    1. They can be gated either to the EKG or peripheral pulse.
    2. Co-registered images are obtained in diastole and systole.
    3. Diastolic and systolic images are added together to produce the angiogram.
    4. Image contrast is based on the long T2 of blood.

    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. Link to Q&A discussion

  2. Which of the following is not a disadvantage of 3D-FSE MRA?
    1. Required use of gadolinium contrast.
    2. Overestimation of stenoses
    3. Vascular pulsation artifacts
    4. Sensitivity to cardiac arrythmias

    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). Link to Q&A discussion

  3. Intravascular contrast in balanced steady-state free precssion (b-SSFP) MRA is primarily related to which property of blood?
    1. High spin-density
    2. Long T1
    3. Long T2
    4. High T2/T1 ratio

    b-SSFP MRA exploits the differences between the relatively high T2/T1 ratio of blood compared to most other tissues. Link to Q&A discussion

  4. What is the main reason b-SSFP MRA sequences are not routinely used in intracranial imaging?
    1. Its spatial resolution is insufficient to resolve the major intracranial vessels.
    2. The signal from intracranial vessels is obscured by high signal from nearby CSF.
    3. Intracranial vessels typically demonstrate turbulent flow which disrupts the SSFP.
    4. Susceptibility artifacts from the skull base produce troublesome zebra-stripe artifacts over most of the brain.

    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. Link to Q&A discussion

  5. The purposes of the inversion pulse(s) used in inflow-enhanced, IR-prepped 3D-SSFP MRA include all of the following except
    1. Nulling of signal from water-containing background tissue.
    2. Nulling of signal from fat
    3. Nulling of signal from venous blood
    4. Hyperpolarization of incoming arterial spins.

    The inversion pulses allow arterial inflow to be relatively accentuated due to background and venous suppression, not because of hyperpolarization. Link to Q&A discussion

  6. What functions do the two inversion pulses perform in an arterial spin labeling (ASL)-prepped MRA?
    1. The first suppresses water in the background and the second suppresses fat in the background.
    2. The first nonselectively suppresses background and the second nulls venous signal.
    3. The first nonselectively tags inflowing spins and the second selectively suppresses background.
    4. The first nonselectively suppresses background and the second selectively tags inflowing spins.

    The simplest form of MRA with ASL is called the Outflow Method. The sequence begins with two 180°-RF pulses applied in close succession. The first 180°-pulse is non-selective, meaning it inverts the entire background regardless of location. The second 180°-pulse is spatially-selective, applied to restore magnetization in the region from which the "fresh" blood will flow. During the inversion time (TI) interval, this fully magnetized ("fresh") blood will enter the anatomic area of interest. Signal generation is then initiated using either a 3D balanced-SSFP or FSE sequence to produce the MRA. Link to Q&A discussion

  7. Which of the following statements about the Quiescent-Interval Single-Shot (QISS) MRA is incorrect?
    1. It does not require cardiac gating.
    2. It does not utilize gadolinium contrast.
    3. It is primarily used for extremity MRA
    4. Unsaturated blood enters the imaged slice during the quiescent interval (QI)

    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. Link to Q&A discussion

  8. Which of the following statements about contrast-enhanced (CE)-MRA is false?
    1. If scanning is performed too early after injection, inadequate vascular visualization may result.
    2. Scanning performed too late after injection may result in venous contamination.
    3. If you incorrectly time the bolus on the first acquisition, you can wait 10 minutes and repeat the injection.
    4. Signal generation is typically performed using a 3D T1-weighted spoiled gradient echo sequence with short TR and TE.

    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. Link to Q&A discussion

  9. What is fluoroscopic triggering for MRA?
    1. A method that uses information from an x-ray fluoroscope to assist in timing of the gadolinium bolus.
    2. A method to estimate timing of arrival of a small (1-2 ml) test bolus of gadolinium.
    3. A 3D-phase contrast method to estimate the distribution of contrast throughout the entire imaging volume.
    4. A method providing a “fluoroscopic-like” MR image during transit of a full contrast bolus at which time the MRA acquisition can begin.

    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. Link to Q&A discussion

  10. The preferred k-space sampling method used for most 3D-CE-MRA sequences is called
    1. Elliptical-centric ordering
    2. Linear ordering
    3. Sequential ordering
    4. Stochastic ordering

    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. Link to Q&A discussion

  11. What type of k-space sampling is used in modern time-resolved MRA sequences like TRICKS and TWIST?
    1. Zig-zag
    2. Cartesian
    3. Radial
    4. Spiral

    Modern time-resolved MRA techniques typically use radial sampling schemes, acquiring 3D k-space in segmented round or oval "cylinders". Link to Q&A discussion

  12. Which technical component is not a feature used in modern time-resolved MRA sequences like TRICKS and TWIST?
    1. 3D-SSFP acquisition
    2. Both phase- and read-conjugate symmetry
    3. Elliptical-centric ordering
    4. Parallel imaging

    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. Link to Q&A discussion

  13. What causes the subclavian artery “pseudo-stenosis” artifact on CE-MRA?
    1. Compression of the subclavian artery by the subclavian vein
    2. Susceptibility effects due to residual gadolinium in the subclavian vein
    3. Turbulence at its junction with the axillary artery
    4. Reflux due to retrograde flow from the vertebral artery into the subclavian artery

    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. Link to Q&A discussion

  14. What is the cause of the ringing (Maki) artifact on CE-MRA?
    1. Gibbs (truncation) phenomenon
    2. Central region of k-space scanned before arrival of the contrast bolus
    3. Central region of k-space scanned too long after arrival of contrast bolus
    4. Vascular pulsation

    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. Link to Q&A discussion

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Cardiac MRI - Anatomy

  1. Which cardiac chambers are typically imaged on the short-axis view?
    1. RA and RV
    2. RA and LA
    3. LA and LV
    4. RV and LV

    The short axis view is typically used to show the left and right ventricles. Link to Q&A discussion

  2. What structure is optimally displayed on the so-called “candy-cane” view?
    1. Thoracic aorta
    2. Circumflex artery
    3. Left main coronary artery
    4. Right coronary artery

    The candy-cane view is an oblique sagittal section that lays out the ascending, transverse, and descending thoracic aorta and its proximal branches. Link to Q&A discussion

  3. Why might one wish to start two IV’s prior to MRI if stress testing is being performed?
    1. The second serves as backup in case the first IV fails.
    2. The total amount of fluid and medications required during the exam exceed the capacity of a single average-bore IV.
    3. Gadolinium contrast and adenosine cannot be given through the same line.
    4. The second IV is needed for blood sampling during the exam.

    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. Link to Q&A discussion

  4. Which of the following foods and medications should be discontinued at least 12-24 hours before a stress MRI?
    1. Nitroglycerin
    2. Calcium-channel blockers
    3. Caffeinated beverages
    4. Quinidine

    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. Link to Q&A discussion

  5. What is the most common EKG change noted when a patient is placed in an MRI?
    1. Reduction of the R-wave
    2. Inversion of the R-wave
    3. Elevation of the T-wave
    4. ST-segment elevation

    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. Link to Q&A discussion

  6. What is the cause of the EKG changes described above?
    1. Ionic currents induced by thoracic blood flow
    2. Susceptibility effects
    3. Stimulation of accessory cardiac conduction pathways
    4. Induced currents in the EKG leads

    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. Link to Q&A discussion

  7. Which EKG wave is primarily used for cardiac triggering?
    1. P-wave
    2. Q-wave
    3. R-wave
    4. T-wave

    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. Link to Q&A discussion

  8. The R-wave corresponds to what cardiac event?
    1. Beginning of atrial contraction
    2. Beginning of ventricular systole
    3. Peak contraction of the ventricle
    4. Beginning of ventricular diastole

    The R-wave coincides with the beginning of ventricular systole. Link to Q&A discussion

  9. If the heart rate is 100 bpm, what is the length of the R-R interval in milliseconds?
    1. 60 ms
    2. 100 ms
    3. 600 ms
    4. 1000 ms

    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. Link to Q&A discussion

  10. 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?
    1. 600 ms
    2. 900 ms
    3. 1200 ms
    4. 1800 ms

    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. Link to Q&A discussion

  11. Continuing the above example in the patient with HR = 100 bpm, what would be the TR if a gating factor of 4 were chosen?
    1. 125 ms
    2. 600 ms
    3. 1200 ms
    4. 2400 ms

    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. Link to Q&A discussion

  12. In a gated study, the time between the first R-wave and the beginning of data acquisition is known as the
    1. Trigger window
    2. Acquisition window
    3. Trigger delay
    4. Quiescent interval

    Trigger delay is the time interval between the first R-wave and the beginning of data acquisition. Link to Q&A discussion

  13. Which of the following is not an advantage of retrospective gating compared to prospective gating?
    1. TR is not restricted to be a multiple of the R-R interval
    2. Data acquired during arrythmias can be rejected.
    3. Data acquired during patient motion can be rejected.
    4. Magnetohydrodynamic distortions in the EKG can be corrected.

    All are true advantages except (d). Link to Q&A discussion

  14. For cardiac imaging navigator pulses are most commonly placed
    1. On the dome of the right hemidiaphragm
    2. On the dome of the left hemidiaphragm
    3. On the left ventricle
    4. On the chest wall

    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. Link to Q&A discussion

  15. Which one of the following statements about double IR sequences for cardiac imaging is true?
    1. The first 180°-pulse is spatially selective, while the second 180°-pulse is non-selective.
    2. Blood suppression requires outside blood flowing in and displacing blood initially within the slice.
    3. Both blood and fat signals are suppressed.
    4. Short TI values are required when the heart rate is slow.

    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. Link to Q&A discussion

  16. An advantage of triple IR over double IR for cardiac imaging is
    1. Suppression of pericardial and mediastinal fat
    2. Shorter imaging times
    3. More freedom on choice of TI values
    4. Improved T1 contrast

    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. Link to Q&A discussion

  17. 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?
    1. 15
    2. 17
    3. 19
    4. 21

    There are 6 basal, 6 middle and 5 apical segments adding to a total of 17. Link to Q&A discussion

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