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MRI exam > MRA + special sequences > Flashcards

MRA + special sequences Flashcards

1
Q

Laminar flow

A

typical pattern of flow which varies from slow at the vessel wall to fast at the centre

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2
Q

why is laminar flow faster at the centre of the vessel
A) higher friction from other blood
B) because it flows slower in the periphery due to friction with the vessel wall

A

B

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3
Q

Turbulent flow

A

random fluctuations in velocity

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4
Q

vortex flow

A

high velocity flow centrally and spiralling for near the walls

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5
Q

Where is vortex flow more common
A) before a stenosis
B) after a stenosis

A

b

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6
Q

stagnant flow

A

flow that is so slow is behaves like stationary tissue

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7
Q

how does presaturation help in MRA
A) suppress unwanted signal flowing in a particular direction
B) enhance signal due to excitement of nuclei

A

A

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8
Q

What MRA uses thinnest slices

A

2D TOF

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9
Q

normal flow demonstrated by a parabolic blood flow curve is
A) laminar
B) accelerated
C) vortex
D) turbulent

A

A
normal blood flow is when the flow at the centre of the vessel is a greater velocity of that of the flow towards the vessel walls

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10
Q

Blood flow at the area of stenosis is
A) laminar
B) accelerated
C) vortex
D) turbulent

A

B

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11
Q

Swirling blood just past the area of stenosis
A) laminar
B) accelerated
C) vortex
D) turbulent

A

C

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12
Q

normal blood flow is
A) laminar
B) accelerated
C) vortex
D) turbulent

A

D

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13
Q

A major advantage of MRA over conventional angiography is
A) images with both T1 and T2 weightings can be produced
B) multiple views can be produced from a single acquisition
C) much smaller catheters can be used
D) less ionising radiation is used

A

B

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14
Q

MRA sequence least sensitive to flow is
A) 3D PC MRA
B) 3D TOF
C) 2D PC
D) 3D TOF

A

B

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15
Q

MRA sequences most sensitive to small vessels
A) 3D PC MRA
B) 3D TOF
C) 2D PC
D) 3D TOF

A

B

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16
Q

MRA sequence sensitive to flow direction
A) 3D PC MRA
B) 3D TOF
C) 2D TOF
D) multislice vascular

A

A

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17
Q

MRA sequence sensitive to flow velocity
A) 3D PC MRA
B) 3D TOF
C) 2D TOF
D) multislice vascular

A

A

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18
Q

signal intensity on TOF MRA is related to
A) Gadolinium
B) flow related enhancement
C) velocity induced phase shift
D) restricted diffusion

A

B

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19
Q

signal intensity on PC MRA is related to
A) Gadolinium
B) flow related enhancement
C) velocity induced phase shift
D) restricted diffusion

A

C

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20
Q

signal in diffusion sequences is related to
A) Gadolinium
B) flow related enhancement
C) velocity induced phase shift
D) restricted diffusion

A

D

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21
Q

which MRA technique is is better for the visualisation of slow flow

A

2D TOF

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22
Q

which MRA technique is better for visualisation of smaller vessels

A

3D TOF

23
Q

which MRA technique uses T1 GE with TR and flip angle selection

A

TOF MRA

24
Q

Which MRA technique uses T2 GE

A

PC MRA

25
Q

which MRA technique allows for visualisation of flow velocity and flow direction

A

PC MRA

26
Q

how does PC MRA allow for visualisation of flow velocity and direction

A

use of VENC factors

27
Q

what does a low VENC evaluate

A

slow flow

28
Q

what does a high VENC evaluate

A

high flow

29
Q

the removal of signal from vessels in an MRA sequence is achieved by
a) gradient moment nulling
b) spatial presaturation
c) spectral presaturation
d) a and b

A

b

30
Q

what is important in MRA sequences to minimise loss of signal due to dephasing within a voxel
A) long TR
B) small voxel
C) short TE
D) b and c

A

D
- longer TE allows for more intravoxel dephasing
- large voxels allow for higher inhomogeneity ad increase dephasing

31
Q

blood flow velocities are greatest
A) further away from the heart
B) at vessel wall
C) at the centre of the vessel
D) in a 3D TOF

A

c

32
Q

single order gradient moment nulling does not compensate for
A) accelerated flow
B) reverse flow
C) constant velocity flow
D) a and b

A

D: SOGMN compensates for constant flow

33
Q

in a spin echo flowing blood is seen as a signal void because
A) TE is too long to image flow
B) TR used is oo long to image flow
C) 90 and 180 pulses are both slice selective
D) flip angle is always 90
E) a and c

A

E

34
Q

at an area of stenosis the velocity of blood flowing at the centre is
A) increased
B) decreased
C) reversed
D) unaffected

A

A

35
Q

in TOF tissue is HYPOintense compared to flowing blood because
A) T2 effects
B) T2* effects
C) saturation effects
D) inhomogeneity

A

C

36
Q

in TOF flowing blood is hyperintense compared to stationary tissue because
A) T2 effects
B) coil being used
C) sat pulse used
D) flow related enhancement

A

D

37
Q

PC techniques produce images where the signal intensity of the vessel is dependant on
A) velocity of flowing blood
B) T1 of tissue
C) FOV
D) # of PE’s

A

A

38
Q

with PC it is possible to determine the
A) size of lumen
B) direction of flow
C) temporal displacement of vessel
D)% stenosis

A

B

39
Q

advantage of 3D TOF vs 2D TOF
A) determine blood flow velocity
B) shorten imaging time
C) visualise smaller vessels
D) reduce signal from stationary tissue

A

C

40
Q

advantage of 2D TOF vs 3D TOF
A) image a larger vol of tissue without saturation of flowing blood
B) determine % stenosis
C) better image reverse flow
D) image a clot without showing slow flow around it

A

A

41
Q

cardiac cine utilises
A) IR
B) SE
C) GE
D) FSE

A

C

42
Q

each frame in a cardiac cine displays the heart in
A) various imaging planes
B) with various degrees of spatial resolution
C) from a different view point
D) in different phases of the cardiac cycle

A

D

43
Q

main purpose of cine is to
A) visualise motion and function
B) visualise slow flow
C) measure muscle strength
D) impress drs

A

A

44
Q

what would show the greatest amount of diffusion
A) b-750
B) b-450
C) b- 825
D) b-1100

A

D

45
Q

what is the purpose of the ADC map
A) reduce diffusion effects
B) eliminate T2 shine through
C) increase SNR
D) reduce T1 weighting

A

B

46
Q

changing the b value alters the
A) amplitude, timing and duration of the diffusion gradients
B) amplitude of the phase encoding gradients
C) length of the read out gradient
D) spatial resolution

A

A

47
Q

when performing a dynamic perfusion scan of the brain with gad, the result of the T2* shortening is
A) Increased MR contrast
B) Reduced MR signal
C) increased acquisition time
D) increased chemical shift

A

B

48
Q

basic MR principle with spectroscopy is
A) faradays law of induction
B) chemical shift
C) flow related enhancement
D) the BOLD effect

A

B

49
Q

after 3D TOF using a MIP technique which of the following can appear bright and mimic flow in a vessel
A) tissues with long T2 relaxation
B) tissues with very short T1 relaxation times
C) polycystic astrocytoma
D) tissues with short T2 relaxation

A

B

50
Q

intrinsic contrast mechanism for fMRI is
A) faradays law of induction
B) chemical shift
C) flow related enhancement
D) the BOLD effect

A

D

51
Q

what does BOLD stand for

A

blood oxygen level dependant

52
Q

all the of following techniques can be used to optimally start a contrast enhanced MRA except
A) automated bolus detection
B) test bolus
C) centric k- space filling
D) real time triggering

A

C

53
Q

to reconstruct an image acquired with parallel imaging, which of the following may be required
A) test bolus
B) reference or calibration scan
C) back projection
D) half fourier acquisition

A

B

54
Q

when using parallel imaging to reduce scan time, which of the following is always true
A) scan time reduced, spatial res increased
B) spatial res reduced as acceleration factor increases
C) SNR is not affected unless acceleration factor exceeds 2
D) SNR is reduced, spatial resolution is unaffected

A

D

MRI exam (14 decks)

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