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MRI Scan Principles Q > pulse sequences > Flashcards

pulse sequences Flashcards

1
Q

In a dual contrast spin echo sequence with echo times of 25ms and 90ms, the second echo image has __________ than the first echo image
I. more T2 contrast
II. lower signal-to-noise ratio
III. more T1 contrast

A

I & II only

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2
Q

A fast spin echo sequence is faster than a conventional spin echo pulse sequence because:

A

Several echoes for each slice are collected during each TR period

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3
Q

Lengthening TR with a short TE in a spin echo sequence will

A

Increase proton density weighting

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4
Q

Conventional spin echo sequences begin with a __________ RF excitation pulse.

A. 25°

B. 45°

C. 180°

D. None of the above

A

None of the above

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5
Q

Which of the following echo train lengths generate a set of images with the greatest signal-to-noise, assuming all other parameters are the same?

A

3 ETL

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6
Q

What is the correct scan time for a spin echo sequence with the following parameters: TR 500 ms, TE 30 ms, matrix 208 x 208, 2 NEX, FOV 200mm?

A

3 minutes 28 seconds
Scan time — TR x Phase matrix x NEX = Scan time in milliseconds, ÷ 1000 to calculate scan time in seconds.

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7
Q

Which of the following echo train lengths generates images in the shortest amount of time?

A

16 ETL
Scan time formula — TR x Matrix x NEX ÷ ETL…. More ETL = faster scan time

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8
Q

For a given number of slices, which of the following pulse sequences uses the most 180° RF pulses during each TR period?

A

Dual contrast spin echo

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9
Q

Each train of echoes has what effect on the pulse sequence in a fast spin echo?

A. Increases SAR absorption
B. Reduces scan time
C. Lowers SNR
D. All of the above

A

All of the above

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10
Q

Which RF pulse is always absent in a gradient echo sequence

A

180° refocusing pulse

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11
Q

The fastest sequence commonly and currently available is

A

Echo planar imaging

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12
Q

When performing a gradient echo pulse sequence, what is used to refocus the protons and create the echo

A

Gradient coils

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13
Q

A pulse sequence that begins with a 180° RF pulse, followed by a 90° RF excitation pulse, would be a(n

A

Inversion recovery

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14
Q

All of the following are types of inversion recovery sequences EXCEPT:

A

DWI

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15
Q

In an inversion recovery sequence, the time interval between the 180° RF pulse and the 90° RF pulse is the:

A

TI

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16
Q

A STIR sequence with a TI time of 160 ms will null signal from fat at what field strength?

A

1.5 Tesla

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17
Q

In which of the following pulse sequences would you expect to find the shortest TR?

A

Gradient echo

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18
Q

The gradient that is on during the production of the echo is the:

A

Frequency encoding gradient

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19
Q

In order to produce an echo in a gradient echo pulse sequence, a ___________ is used

A. RF pulse

B. Gradient field

C. Combination of two RF pulses

D. 180° pulse, then 90° pulse

E. All of the above

F. A & B only

A

A & B only

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20
Q

: In a Fast Spin Echo sequence, the effective TE are the echoes that are encoded:

A

With a low amplitude phase encoding gradient

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21
Q

: In a fast spin echo pulse sequence, if the TSE factor (echo train length) is increased by a factor of 3, the scan time will be:

A

Three times faster
In a fast spin echo pulse sequence, if the TSE factor

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22
Q

In a spin echo sequence, the time between the 90° RF pulse and the 180° RF pulse is known as the:

A

1/2 TE

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23
Q

The timing of RF pulses in an MRI pulse sequence controls:

A

Image contrast

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24
Q

Which RF pulse refocuses a decaying spin echo?

A

180°

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25
Q

: As the TE is increased,
I. The available number of slices is increased
II. The available number of slices is decreased
III. SNR increases
IV. T1 contrast is maximized

A

II only

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26
Q

As the TR is increased,
I. SNR is increased
II. Available number of slices is increased
III. T2 information is maximized

A

I and II only

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27
Q

Which of the following sequences is the most insensitive to magnetic field inhomogeneity?

A

Spin echo

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28
Q

CSF suppression is performed with which type of technique?

A

FLAIR

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29
Q

The echo time is the

A

Time between the 90º RF pulse and the peak of the signal in the receiver coil

30
Q

The repetition time is the

A

Time between two 90º RF pulses

31
Q

Which of the following combinations of flip angle (FA) and TR would produce a T2 weighted gradient echo?

A

450 TR; 30º flip angle

32
Q

: In a spin echo pulse sequence, an echo is produced from:

A

A combination of two or more RF pulses

33
Q

Image 73 is a diagram of which pulse sequence

A

Fast spin echo

34
Q

Letter A in Image 73 represents:

A

Radiofrequency (RF)

35
Q

Letter B in Image 73 represents

A

Slice select gradient

36
Q

Letter C in Image 73 represents

A

Phase encoding gradient

37
Q

Letter D in Image 73 represents

A

Frequency encoding gradient

38
Q

Letter E in Image 73 represents:

A

MR signal

39
Q

Letter F in Image 73 represents

A

180º RF pulses (echo train)

40
Q

Image 74 is a diagram of which pulse sequence

A

Gradient echo

41
Q

Letter A in Image 74 represents:

A

Radiofrequency (RF)

42
Q

: Letter B in Image 74 represents

A

Slice select gradient

43
Q

: Letter C in Image 74 represents

A

Phase encoding gradient

44
Q

Letter D in Image 74 represents

A

Frequency encoding gradient

45
Q

Letter F in Image 74 represents

A

Echo time (TE)

46
Q

Letter G in Image 74 represents

A

Tau (1/2 TE

47
Q

: Letter H in Image 74 represents

A

Peak signal for echo

48
Q

Image 75 is a diagram of which pulse sequence

A

Inversion recovery

49
Q

Letter A in Image 75 represents:

A

Inverting 180º RF pulse

50
Q

: Letter B in Image 75 represents

A

Slice select gradient

51
Q

Letter C in Image 75 represents

A

Phase encoding gradient

52
Q

: Letter D in Image 75 represents

A

Frequency encoding gradient

53
Q

Letter E in Image 75 represents:

A

Inversion time (TI)

54
Q

Letter F in Image 75 represents

A

Echo time (TE)

55
Q

Letter G in Image 75 represents

A

: Phase encoding step

56
Q

Letter H in Image 75 represents

A

180º RF pulse (refocussing

57
Q

Letter K in Image 75 represents:

A

90º RF excitation pulse

58
Q

Image 76 is a diagram of which pulse sequence

A

Spin echo

59
Q

Letter A in Image 76 represents:

A

Radiofrequency (RF)

60
Q

Letter B in Image 76 represents

A

Slice select gradient

61
Q

Letter C in Image 76 represents

A

Phase encoding gradient

62
Q

Letter D in Image 76 represents

A

Frequency encoding gradient

63
Q

Letter E in Image 76 represents:

A

MR signal

64
Q

Letter F in Image 76 represents

A

: Echo time (TE)

65
Q

Letter G in Image 76 represents:

A

Refocussing 180º RF pulse

66
Q

Image 77 is a diagram of which pulse sequence

A

Dual echo spin echo

67
Q

Letter E in Image 77 represents

A

TE 1 (shorter TE)

68
Q

Letter F in Image 77 represents

A

TE 2 (longer TE)

69
Q

Fast spin echo sequences are fast because

A

More than 1 line of k-space is acquired in each TR period

70
Q

What specifically is a SPGR sequence spoiling

A

: Transverse magnetization

MRI Scan Principles Q (6 decks)

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