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MRI exam > sequence parameters and options > Flashcards

sequence parameters and options Flashcards

1
Q

time between excitation pulses is
A) T1
B) TE
C) TR
D) PR

A

C

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2
Q

in SE the time between the 90 and 180 RF pulse is
A) TE
B) TR
C) TI
D) 1/2 TE

A

D

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3
Q

presaturation pulses are often used to
A) improve spatial resolution
B) reduce flow artefacts
C) reduce scan time
D) turn flowing blood bright

A

B

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4
Q

presaturation pulses usually occur
A) prior to the excitation pulse
B) after the 180 pulse
C) between the 90 and 180 pulses
D) prior to the TE

A

A

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5
Q

gradient echo uses flip angles
A) less than 90
B) that vary between pulse repetitions
C) to control saturation effects
D) to reduce SAR for larger pts

A

c. increasing flip angle will increase the saturation effects

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6
Q

complete saturation is when
A) not enough time is given to allow for T2 decay
B) the image becomes brighter
C) longitudinal relaxation is not given enough time to recover between excitations
D) proton density effects predominate

A

C

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7
Q

increasing the TE
A) increases contrast based on T2 relaxation of tissues
B) reduces contrast based on T2 relaxation of tissues
C) reduces contrast based on T1 relaxation of tissues
D) a and c

A

A

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8
Q

reducing the TR down to or below the T1 relaxation time
A) decreases SNR
B) reduces contrast based on T2 times of tissue
C) increases saturation effects
D) a and c

A

D

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9
Q

reducing the TE
A) increases contrast based on T1 relaxation times
B) increases spin density contrast
C) reduces saturation effects
D) reduces contrast based on T2

A

D

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10
Q

as the TR increases
A) SNR increases up to a point
B) SNR decreases
C) SNR is not affected
D) TE increases

A

a

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11
Q

as TE increases
A) SNR increases
B) SNR decreases
C) SNR is not affected
D) TR increases

A

B

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12
Q

in GE sequences, reducing the flip angle while holding the TR constant reduces
A) T2*
B) spin density contrast
C) saturation
D) scan time

A

C

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13
Q

2D conventional spin echo scan time =
A) time x # PEs x TR
B) TR x FOV x NSA
C) TR x # slices x NSA
D) TR x #PEs x NSA

A

d

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14
Q

in IR the image contrast is controlled by
A) TR and TE
B) TI
C) TI and TE
D) TR, TE and TI

A

D

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15
Q

in IR the timing between the 180 and the 90 pulses is known as
A) TE
B) TR
C) TI
D) T1

A

C

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16
Q

another name for TI is
A) alpha
B) theta
C) sigma
D) tau

A

D

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17
Q

a short TI STIR can suppress signal from
A) fat
B) water
C) gadolinium enhancing lesion
D) a and c

A

d. gad shortens the T1 time of tissue close to the relaxation time of fat and thus these tissues can also be suppressed with fat

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18
Q

decreasing the receiver BW
A) decreases SNR
B) inverts SNR
C) increases SNR
D) has no effect

A

c

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19
Q

decreasing receiver BW
A) increases readout time
B) inverts chemical shift
C) reduces chemical shift
D) has no effect on chemical shift

A

A

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20
Q

decreasing the receiver BW
A) increases readout time
B) inverts readout time
C) reduces readout time
D) has no effect on readout time

A

A

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21
Q

decreasing the receiver BW
A) decreases susceptibility artifact
B) inverts susceptibility artifact
C) increased susceptibility artifact
D) has no effect on the susceptibility artifact

A

c

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22
Q

decreasing the receiver BW
A) decreases # of slices
B) inverts # of slices
C) increases # of slices
D) has no effect of # of slices

A

A

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23
Q

increasing the receiver BW
A) decreases ETL
B) inverts ETL
C) increases ETL
D) has no effect on ETL

A

d

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24
Q

the time during which the frequency encoding gradient is on
A) increases with a reduction in receiver BW
B) decreases with a reduction in receiver BW
C) is not affected by a reduction in the receiver BW
D) cannot be changed by a reduction in the receiver BW

A

A

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25
Q

in a SE multi echo is is possible to create multiple images, each with different amounts of
A) T1 weighting
B) PE
C) T2 weighting
D) spatial resolution

A

C

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26
Q

SNR will increase in a 3D sequence with an increase in
A) FOV
B) # slices
C) TE
D) a and b

A

d. # of slices increases volume of tissue excited and increasing FOV increases the voxel vol which also increases the SNR

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27
Q

between slices in 2D acquisitions it generally requires
A) wait time
B) gradient refocussing
C) gaps
D) inversion time

A

c. because the RF pulse is not perfect adjacent slices are slightly affected this can cause cross talk and reduce the SNR and contrast

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28
Q

doubling the NSA will
A) decrease SNR
B) increase SNR by the square root of 2
C) double SNR
D) not affect SNR

A

b. SNR= √NSA thus √2=1.41

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29
Q

increasing # of phase encodings will produce an image with
A) increased voxel volume
B) decreased voxel volume
C) unchanged voxel volume
D) higher SNR

A

b

30
Q

reducing NSA will reduce scan time and
A) decrease SNR
B) increase SNR by a factor of 1.41
C) not affect SNR
D) double SNR

A

a

31
Q

how does SNR and NSA relate

A

SNR√NSA

32
Q

doubling the NSA will increase SNR by a factor of
A) 2
B) 4
C)1.6
D)1.41

A

d

33
Q

reducing the FOV by a factor of 2 will reduce the voxel volume by a factor of
A) √2
B) 2
C) 8
D)4

A

d. FOV affects the voxel volume in 2 dimensions (phase and frequency)

34
Q

If a STIR sequence is using a TR of 3000, TE of 20 and TI of 140 it produces an image with dark fat and bright water. the contrast of the image is primarily based on
A) Flow
B) T1
C) T2
D) Dephasing

A

B

35
Q

In choosing the direction of phase encoding, the technologist usually considers the direction in which the
A) most signal is needed
B) scan time will not be affected
C) motion artifacts traverse the least of the tissue or AOI
D) resolution will not be distorted

A

C

36
Q

A chemical or spectral fat suppression will suppress the signal from the fat based on
A) precessional f of fat
B) amount of fat in the target slice
C) T2 relaxation time of fat
D) a and c

A

a

37
Q

increasing the slice thickness from 5mm to 10mm the SNR
A) inc by factor 2
B) inc by factor 4
C) is not affected
D) decreases by factor 2

A

a

38
Q

increasing the # of PE’s from 128 to 256 the SNR
A) increases
B) inverts
C) not affected
D) decreases

A

d

39
Q

gradient moment nulling is most effective when correcting from motion induced signal loss from
A) pulsatile flow
B) no flow
C) slow constant flow
D) magnetic field inhomogeneity

A

c

40
Q

to rephase signal from moving spins, gradient moment nulling use a
A) RF pulse
B) gradient
C) series of short, rapid pulses that are strategically timed
D) flow encoding gradient

A

b

41
Q

when using conventional spin echo multislice sequence, the # of slices allowed when increasing the TR
A) decreases
B) is not affected
C) increased by a factor of TE/TR
D) doubles

A

c

42
Q

using a conventional spin echo multislice sequence, the # of slices allowed when increasing the TE from 20-40ms
A) decreases
B) is not affected
C) increases by a factor of TR x TE
D) doubles

A

a

43
Q

using a 3D acquisition, the number of slices allowed when increasing the TR
A) decreases
B) is not affected
C) increases by a factor of TR/2
D) doubles the scan time

A

b

44
Q

using a 3D acquisition, increasing the number of slices from 64 to 128
A) reduces the scan time
B) has no effect on scan time
C) increases scan time by a factor of 1.41
D) doubles the scan time

A

d

45
Q

increasing the matrix in f encoding direction from 256 to 512 will
A) reduce scan time
B) have no effect on the scan time
C) increase the time by a factor of 256/512
D) double scan time

A

b

46
Q

the effective TE in a FSE determines the
A) image contrast
B) scan time
C) spatial resolution
D) # of f samples

A

a

47
Q

in a FSE the central lines of k space is associated with
A) images spatial resolution
B) TR
C) effective TE
D) scan time

A

c

48
Q

when triggering a scan from the patients ECG the TR of the sequence is determined by
A) # of PE’s
B) # of phases of heart cycle being sampled
C) # of FE’s
D) pts heart rate

A

d

49
Q

increasing the TR
A) increases scan time
B) inverts scan time
C) does not affect scan time
D) decreases scan time

A

a

50
Q

increasing TE
A) increases scan time
B) inverts scan time
C) does not affect scan time
D) decreases scan time

A

c

51
Q

increasing the # of slices in 2D acquisitions
A) increases scan time
B) inverts scan time
C) does not affect scan time
D) decreases scan time

A

c

52
Q

for a tissue with a given T1 relaxation time and TR, the flip angle which will result in the maximum signal for that tissue is
A) 90
B) 180
C) 45
D) the Ernst angle

A

D

53
Q

increasing FOV
A) increase scan time
B) inverts scan time
C) does not affect scan time
D) decreases scan time

A

c

54
Q

increasing the phase matrix
A) increase scan time
B) inverts scan time
C) does not affect scan time
D) decreases scan time

A

a

55
Q

increasing slice thickness
A) increase scan time
B) inverts scan time
C) does not affect scan time
D) decreases scan time

A

c

56
Q

increasing the NSA
A) increases scan time
B) inverts scan time
C) does not affect scan time
D) decreases scan time

A

a

57
Q

increasing the slice thickness
A) increases SNR
B) invers SNR
C) does not affect SNR
D) decreases SNR

A

a

58
Q

increasing the matrix
A) increases SNR
B) invert SNR
C) does not affect SNR
D) decreases SNR

A

d

59
Q

increasing the flip angle
A) increases SNR up to the Ernst angle
B) inverts SNR
C) does not affect SNR
D)always increases SNR

A

a

60
Q

reducing the ETL
A) increases scan time
B) inverts scan time
C) does not affect scan time
D) decreases scan time

A

a

61
Q

reducing the TE
A) increases SNR
B) inverts SNR
C) does not affect SNR
D) decreases SNR

A

a

62
Q

reducing the TE yields the image with
A) more T1 information
B) less T1 information
C) more T2 information
D) less T2 information

A

d

63
Q

increasing the TR yields image with
A) more T1 information
B) less T1 information
C) more T2 information
D) less T2 information

A

b

64
Q

increasing the TE
A) more T1 information
B) less T1 information
C) more T2 information
D) less T2 information

A

c

65
Q

reducing the TR yields the image with
A) more T1 information
B) less T1 information
C) more T2 information
D) less T2 information

A

a

66
Q

TE controls which weighting

A

T2

67
Q

TR controls which weighting

A

T1

68
Q

reducing the flip angle yields an image with
A) more T1 information
B) less T1 information
C) more T2 information
D) less T2 information

A

b

69
Q

Increasing the flip angle
A) more T1 information
B) less T1 information
C) more T2 information
D) less T2 information

A

a

70
Q

what contrast parameter does the flip angle controll

A

T1

MRI exam (14 decks)

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