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MRI in practice 5th ed. > Chapter 8.2 > Flashcards

Chapter 8.2 Flashcards

Flow phenomena & MRA

1
Q

When limited coverage is needed (ex: evaluation of COW for an acute cerebral infarction),

a. MOTSA is used
b. 2D-TOF is used
c. 2D-TOF followed by MOTSA is used
d. A single 3D-TOF slab is used

A

d. A single 3D-TOF slab is used

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2
Q

When greater coverage is required (ex: evaluation of carotid artery stenosis)

a. A single 3D-TOF slab is used
b. Multiple 3D-TOF slabs are used
c. MOTSA is used
d. Phase contrast MRA is used

A

c. MOTSA is used

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3
Q

Once a series of 2D or 3D slices has been acquired, to be displayed in angiographic format,

a. They are viewed directly as 64 separate images
b. They are scrolled consecutively on a workstation
c. A maximum intensity projection (MIP) algorithm is generally used
d. Venetian blind artifacts must be produced

A

c. A maximum intensity projection (MIP) algorithm is generally used

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4
Q

One potential problem with the MIP algorithm is that it includes anything that is:

a. Bright on the T1-weighted source images, including subacute hemorrhage and fat
b. Dark on the T1-weighted source images, including chronic hemorrhage and cysts
c. Bright on the T2-weighted source images, including hyperacute hemorrhage and fibrous tissue
d. Dark on the T1-weighted source images, except those entities that enhance with gadolinium

A

a. Bright on the T1-weighted source images, including subacute hemorrhage and fat

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5
Q

Contrast enhanced MRA depends upon _______________ to produce the bright signal in the flowing blood:

a. The VENC
b. Inflow enhancement
c. Short T1 relaxation time
d. Short T2 relaxation time

A

c. Short T1 relaxation time

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6
Q

In PC MRA, the strength of the phase encoding gradient is determined by setting a parameter called the:

a. Sat pulse
b. Slab thickness
c. Xyz gradient
d. VENC

A

d. VENC

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7
Q

A major advantage of MRA over conventional angiography is that:

a. Images with heavy T1 and T2 weighting can be produced
b. Multiple views can be produced from a single acquisition
c. Much smaller catheters are used
d. Less ionizing radiation is used

A

b. Multiple views can be produced from a single acquisition

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8
Q

Excellent signal and background tissue suppression of the renal arteries in a single breath hold can be achieved by:

a. 3D phase contrast (PC)
b. 3D inflow (TOF)
c. 2D PC
d. Contrast enhanced MRA

A

d. Contrast enhanced MRA

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9
Q

The MRA sequence that is MOST sensitive to smaller vessels is:

a. 3D phase contrast (PC)
b. 3D inflow (TOF)
c. 2D PC
d. 2D inflow (TOF)

A

b. 3D inflow (TOF)

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10
Q

The MRA sequence that is MOST sensitive to flow velocity is:

a. 3D phase contrast (PC)
b. 3D inflow (TOF)
c. 2D PC
d. Multi-slice vascular

A

a. 3D phase contrast (PC)

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11
Q

The signal intensity on TOF MRA sequences is related to:

a. Gadolinium
b. Flow-related enhancement
c. Velocity-induced phase shift
d. Restricted diffusion

A

b. Flow-related enhancement

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12
Q

The signal intensity on PC MRA sequences is related to:

a. Gadolinium
b. Flow related enhancement
c. Velocity-induced phase shift
d. Restricted diffusion

A

c. Velocity-induced phase shift

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13
Q

In a phase contrast MRA, it is possible to use the data to determine:

a. Exact size of the vessel lumen
b. Direction of blood flow
c. Temporal displacement of the vessel
d. Percentage stenosis of a lesion

A

b. Direction of blood flow

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14
Q

A major advantage of 3D TOF over 2D TOF is the ability to:

a. Determine blood flow velocities
b. Shorten imaging time
c. Visualize smaller vessels
d. Reduce signal intensity from stationary tissue

A

c. Visualize smaller vessels

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15
Q

A major advantage of 2D TOF over 3D TOF is the ability to:

a. Image a larger area without saturation of flowing blood
b. Determine percentage stenosis in the presence of a lesion
c. Better image reverse flow
d. Image a clot without showing slower flow around it

A

a. Image a larger area without saturation of flowing blood

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16
Q

Images where the signal from blood has been mostly eliminated are known as:

a. Black blood
b. Bright blood
c. Wipe-out
d. Deletion

A

a. Black blood

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17
Q

Which MRA provides the best saturation of stationary tissue?

a. 3D PCA
b. 3D TOF
c. 2D TOF
d. MOTSA

A

a. 3D PCA

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18
Q

_________ MRA sequences can evaluate vasculature with blood flow in multiple directions and with varying flow velocities

a. NEX
b. AVM
c. 2D
d. PC

A

d. PC

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19
Q

In a dual echo sequence, which of the following would result in reduced flow artifact in the second echo?

a. TE 20 and 50 ms
b. TE 20 and 70 ms
c. TE 40 and 80 ms
d. TE 40 and 95 ms

A

c. TE 40 and 80 ms

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20
Q

The magnitude of Entry Slice Phenomena depends on all EXCEPT:

a. Time of repetition
b. Slice number
c. Velocity of flow
d. Direction of flow

A

b. Slice number

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21
Q

Flow artifacts can be reduced by:

a. Gradient moment nulling
b. Spatial presaturation pulses
c. Shortening the TE
d. All of the above

A

d. All of the above

22
Q

The motion of flowing nuclei causes mismapping of signals and results in artifacts know as phase:

a. Disappearance
b. Apparitions
c. Ghosting
d. Shifting

A

c. Ghosting

23
Q

When gradient moment rephasing assumes a constant velocity and direction across the gradient at all times, it is called first order ___________?

a. Motion compensation
b. Kinetic compensation
c. Frozen compensation
d. Time compensation

A

a. Motion compensation

24
Q

Blood flow at the area of a stenosis (vascular narrowing) is known as:

a. Laminar flow
b. Accelerated flow
c. Vortex flow
d. Turbulent flow

A

b. Accelerated flow

25
Q

Normal blood flow is known as:

a. Laminar flow
b. Accelerated flow
c. Vortex flow
d. Turbulent flow

A

a. Laminar flow

26
Q

The swirling blood flow that occurs just past the area of a stenosis is known as:

a. Laminar flow
b. Accelerated flow
c. Vortex flow
d. Turbulent flow

A

c. Vortex flow

27
Q

Blood flow velocities are greatest _______________:

a. Farther away from the heart
b. At the vessel wall
c. At the center of the vessel
d. In a 3D TOF sequence

A

c. At the center of the vessel

28
Q

Single order gradient moment nulling does NOT compensate for:

a. Accelerated flow
b. Reverse flow
c. Slow laminar flow
d. A. and b.

A

d. A and b

29
Q

In a TOF sequence, the tissue is HYPOintense relative to flowing blood because of:

a. T2 effects
b. T2* effects
c. Saturation effects
d. Inhomogeneities

A

c. Saturation effects

30
Q

In a TOF sequence, flowing blood is HYPERintense relative to stationary tissue because of:

a. T2 effects
b. Coil being used
c. Saturation pulse used
d. Flow related enhancement

A

d. Flow related enhancement

31
Q

Even echo rephasing:

a. Reduces intra-voxel dephasing
b. Reduces artifacts on T1 weighted images
c. Reduces artifacts from time of flight
d. Reduces artifacts from entry slice phenomenon

A

a. Reduces intra-voxel dephasing

32
Q

To scan an MRV of the pelvis, the saturation pulse should be placed:

a. Above the heart
b. Above the prescribed slices
c. Below the prescribed slices
d. A and b

A

b. Above the prescribed slices

33
Q

Which of the following does NOT compensate for flow phenomena:

a. Even echo rephasing
b. Spatial resolution
c. Spatial pre-saturation
d. Gradient moment nulling

A

b. Spatial resolution

34
Q

In gradient moment rephasing, which is the correct application of the gradients?

a. Negative, double positive, negative
b. Double positive, negative, negative
c. Positive, double negative, positive
d. Double negative, positive, positive

A

c. Positive, double negative, positive

35
Q

Gradient moment rephasing is MOST effective on:

a. First order motion
b. Fast laminar flow
c. Pulsatile flow
d. A and b

A

a. First order motion

36
Q

With a longer TE in TOF spin echo:

a. More nuclei have received only one pulse
b. Flow related enhancement increases
c. The signal void decreases
d. Both a and c

A

a. More nuclei have received only one pulse

37
Q

For which of the following are pre-saturation pulses NOT recommended:

a. T1 weighted images
b. In between slices in the stack
c. Minimizing ghosting of the aorta
d. Proton density weighted images

A

b. In between slices in the stack

38
Q

Flow phenomena that cause flow artifacts include which of the following:

a. Time of flight
b. Entry slice phenomena
c. Intra-voxel dephasing
d. All of the above

A

d. All of the above

39
Q

Flow that exhibits consistent, but different, velocities across a vessel are what type of flow?

a. Vortex
b. Spiral
c. Laminar
d. Turbulent

A

c. Laminar

40
Q

To do the 2D TOF MRA of carotid arteries, the best orientation for the 2D slices will be:

a. Transverse
b. Oblique axial and sagittal
c. Coronal
d. Sagittal

A

a. Transverse

41
Q

With laminar flow, the flow is the slowest at:

a. The center of the lumen
b. At the vessel wall
c. Between the vessel wall and the center of the lumen
d. None of the above

A

b. At the vessel wall

42
Q

To scan an MRA of the circle of willis, the saturation pulse should be placed:

a. Through the carotid bifurcation
b. Below the heart
c. Just below the prescribed slices
d. Above the corpus callosum

A

d. Above the corpus callosum

43
Q

Spatial pre-saturation nullifies the signal from flowing nuclei to minimize:

a. Entry slice phenomena
b. Time of flight
c. Intra-voxel dephasing
d. A and b only

A

d. A and b only

44
Q

As the velocity of flow increases in TOF spin echo:

a. Flow-related enhancement occurs
b. High velocity signal loss occurs
c. Nothing happens
d. None of the above

A

b. High velocity signal loss occurs

45
Q

As the slice thickness increases in TOF spin echo:

a. Flow-related enhancement increases
b. Flow-related enhancement decreases
c. Signal void decreases
d. Both a and c

A

d. Both a and c

46
Q

Another name for entry slice phenomena is:

a. Intra-voxel dephasing
b. High velocity signal loss
c. Inflow effect
d. None of the above

A

c. Inflow effect

47
Q

The most important factor in determining the magnitude of inflow effect is:

a. TR
b. Slice thickness
c. Velocity of flow
d. Direction of flow

A

d. Direction of flow

48
Q

Entry slice phenomena increases with:

a. A short TR
b. Counter-current flow
c. Decrease in velocity of flow
d. Thick slices

A

b. Counter-current flow

49
Q

Intra-voxel dephasing occurs when:

a. There is even echo rephasing
b. Nuclei within the same voxel are in phase with each other
c. There is gradient moment nulling
d. None of the above

A

d. None of the above

50
Q

A sequence in which two 180-degree pulses are used to saturate blood is called double IR prep. Another way to achieve black blood imaging is to use a T1-weighted image and saturate inflowing spins with a SAT pulse outside the slice stack.

a. True
b. False

A

a. True

MRI in practice 5th ed. (10 decks)

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