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Physics > Chapter 5 > Flashcards

Chapter 5 Flashcards

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1
Q

Parallel imaging is usually used to increase resolution or decrease scan time. (T or F)

A

true

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2
Q

What do T1 images typically best demonstrate?

A

Anatomy

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3
Q

What does STIR stand for? Short ___ Inversion Recovery.

A

tau

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4
Q

SSFP sequences usually produce images that are ___ weighted.

A

T2

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5
Q

What are the advantages of propeller K Space filling?

A

Rapid imaging, increased SNR and CNR, reduced motion artifact.

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6
Q

Which sequence is considered the gold standard for MR imaging

A

Spin Echo

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7
Q

How is time reduced in fast spin echo?

A

Use a turbo factor, Use an echo train

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8
Q

What is Double IR prep used to accomplish?

A

Used to null blood for cardiac imaging

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9
Q

What type of echoes are sampled during SS-FSE?

A

Spin echoes

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10
Q

What artifact can occur as a result of using long echo trains?

A

Image Blurring

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11
Q

When would we be most likely to use a FLAIR sequence?

A

Head or spine studies (to look for periventricular lesions)

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12
Q

Which Fast Inversion Recovery sequence(s) do we often use?

A

FLAIR, STIR

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13
Q

What is the approximate T1 relaxation time of fat at 1T?

A

200 ms

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14
Q

Which of the following statements is true in an incoherent gradient echo sequence?

A

The system discriminates between residual and the most recently created transverse magnetization because it has a different phase value

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15
Q

look at q 16 (quiz)

A

_

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16
Q

look at q 14 (quiz)

A

_

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17
Q

How is K space filled in Fast Gradient Echo Sequences?

A

Keyhole filling,

Centric filling

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18
Q

When would we be most likely to use a STIR sequence?

A

MSK studies (i.e. knee, wrist)

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19
Q

Spin echo pulse sequences are classified according to whether the residual transverse magnetization is in phase (coherent) or out of phase (incoherent). (T or F)

A

False

GRADIENT ECHO sequences are classified according to whether the residual transverse magnetization is in phase (coherent) or out of phase (incoherent). See page 167 in the text for more information.

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20
Q

What is the approximate T1 relaxation time of CSF at 1T?

A

2000 ms

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21
Q

In which of the following sequences is all the transverse magnetization rewound at the end of each TR period?

A

Coherent gradient echo

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22
Q

An inversion recovery pulse sequence begins with which of the following?

A

180 degree inverting pulse

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23
Q

FLAIR stands for Fluid Low Attenuation Inversion Recovery

T or F

A

False

FLAIR stands for Fluid Attenuated Inversion Recovery

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24
Q

STIR sequences should NOT be used in conjunction with contrast enhancement. (T or F)

A

True

STIR sequences should NOT be used in conjunction with contrast enhancement, which shortens the T1 times of enhancing tissues, making them bright. The T1 times of these structures are shortened so that they approach the T1 time of fat. In a STIR sequences therefore, enhancing tissue may also be nulled. See page 158 in the text for more information.

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25
Q

During EPI all the lines of K space are filled during one repetition. (T or F)

A

true

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26
Q

Using a long echo train decreases the SAR. (T or F)

A

False

Using a long echo train significantly increases the SAR by applying so many successive 180 degree pulses. See page 150 in the text for more information.

27
Q

look at q 1, 2, 9, (study guide)

A

_

28
Q

what order is centric filling in K space

A

center lines first, outer last

29
Q

what order is keyhole filling in K space

A

outer first, center after contrast injection

30
Q

what order is EPI k space filling

A

readout gradient switches from pos to neg, phase polarity does not change

31
Q

what order is spiral k space filling

A

readout and phase both switch polarity

32
Q

Generally speaking, gradient echo sequences are faster than spin echo sequences. (T or F)

A

true

33
Q

Which pulse sequence is the gold standard?

A

spin echo

34
Q

What are the two fast inversion recovery sequences that we often use?

A

STIR. Nulls the signal from fat.

FLAIR. Nulls CSF.

35
Q

what are the uses of STIR

A

musculoskeletal

36
Q

what are uses for FLAIR

A

periventricluar lesions

37
Q

coherent gradient echo

A

rewinding. transverse is rewound at end of each TR

38
Q

incoherent gradient echo

A

spoilers. differentiates between residual and most recently created transverse magnetization

39
Q

which is True T2* - angiographic, myelographic or arthrographic effect

A

coherent gradient echo

40
Q

which demonstrate T1 anatomy and pathology and after gadolinium?

A

incoherent gradient echo

41
Q

During which k-space filling are lines filled as a block and rotated about the central axis of k-space, decreasing scan time, increasing the SNR and decreasing motion?

A

propeller

42
Q

Which of the following describes a “steady state” in MRI?

A

Created when the TR is shorter than the relaxation time of tissues. Energy “in” by the FA = energy “out” during the TR

Residual builds in the transverse plane

resultant image is a ratio of T1 to T2

43
Q

What is used to rephase the FID in gradient sequences?

A

a gradient

44
Q

Which type of imaging fills multiple lines of k-space per TR by assigning lines of k-space to coils coupled together, thus acquiring data simultaneously.

A

Parallel imaging. Can be used to reduce scan time or improve resolution.

45
Q

What does this statement describe?

As the area of the gradient under the line equals that above the line, moving spins accumulate a zero change as they pass along the gradients.

A

balanced gradient system

46
Q

double IR prep

A

black blood

47
Q

triple IR prep

A

nulls fat and blood

48
Q

RF spoiling

A

only info from the most recently created magnetization to affect image contrast

49
Q

gradient spoiling

A

residual magnetization is dephase so it is incoherent at beginning of next repition

50
Q

advantage of spin echo

A

good quality, true T2

51
Q

disadvantage of spin echo

A

long scan times

52
Q

T1 most useful to

A

demonstrate anatomy

53
Q

T2 most useful to

A

demonstrate pathology

54
Q

effective TE

A

weighting in fast spin echo bc echoes are generated at different TE times

55
Q

T2*

A

always present to some degree

56
Q

True T2

A

steady state free precession (SSFP)

57
Q

Relaxation times of water

A

2500 ms (for T1 and T2 times)

58
Q

relaxation T1 time of fat

A

200 ms

59
Q

relaxation T2 time of fat

A

100

60
Q

relaxation T1 time of CSF

A

2000 ms

61
Q

relaxation T2 time of CSF

A

300 ms

62
Q

Which pulse sequence are classified according to whether the residual transverse magnetization is in-phase (coherent) or out-of-phase (incoherent)?

A

gradient

63
Q

___: Partial Fourier + fast spin echo. Half the lines are acquired and half are transposed. Reduces SAR but has SNR penalty.

A

single-shot fast spin echo

Physics (15 decks)

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