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MRI QUIZ > Image Safety, Basics and Formation > Flashcards

Image Safety, Basics and Formation Flashcards

1
Q

Spin lattice relaxation is another word for T_ imaging.

A

T1

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2
Q

Spin spin relaxation is another word for T_ imaging.

A

T2

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3
Q

T1 relaxation occurs when the nuclei give up their energy to surround tissue.

True or false

A

True

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4
Q

T1 occurs along the _________ magnetization.

Long or Transverse?

A

longitudinal

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5
Q

T1 Relaxation is the recovery of ___ Longitudinal magnetization.

37 or 63?

A

63%

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6
Q

T2 relaxation time is defined as the time it takes for ____ of the____magnetization to
decay, or the time it takes the spins to de-phase to 37% of their original value.

63% and transverse

A

63% and transverse

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7
Q

Fat has a ____ T1 relaxation and a ____ T2 relaxation time.

A

short and short. It just bounces right back real quickly

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8
Q

Water in fat recovers more rapidly along the long axis ithan water and loses transverse magnetization faster than water.

True or False

A

True

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9
Q

The T1 time of FAT is ____ than water.

Shorter or longer?

A

SHORTER,

therefore fat shows up bright and water shows up dark.

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10
Q

Water has a ____ T1 relaxation and a ____ T2 relaxation time.

A

long t1 and long t2

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11
Q

T1’s use a ___ TR and a ___ TE.

Short or long?

A

T1= short TR + short TE

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12
Q

T2’s use a ____ TR and a ____ TE.

long or short

A

T2= LONG TR + LONG TE

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13
Q

T1s are mostly in control of which kind of imaging? TR or TE?

A

T1’s mainly ruled by TR

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14
Q

T2s are mostly in control of which kind of imaging? TR or TE?

A

T2’s mainly ruled by TE

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15
Q

What is affected when we lower the TR?

A

this will LOWER the SNR

REDUCE scan time

Increase T1 weighting

Reduce the number of slices

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16
Q

What is affected when we increase the TR?

A

will IMPROVE the SNR

INCREASE scan time

REDUCE t1 weighting

Increase the number of slices

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17
Q

When scanning a T1 what is the appropriate range of the TR and TE?

A

(remember T1s are SHORT TR and SHORT TE)

When scanning a T1- TR should be between 350-700 (most places say 400-725)

The TE should be 10-30

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18
Q

When scanning a PD what is the appropriate range of the TR and TE?

A

TR should be 1500-3000 for PD

TE- 10-30 same as T1s

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19
Q

When scanning a T2 what is the appropriate range of the TR and TE?

A

Remember T2=Long Te Long TR

TR should be 2000-6000 (most places say 3000-6000)

TE should be 70-120.

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20
Q

If the TR is doubled then the scan time will ____.

Half or double

A

Double

TR is directly proportional to scan time. So if one goes up the other does too.

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21
Q

Say we have a super crappy patient and we want to decrease our scan time, name a few ways we can do this.

A

Decrease Tr
Reduce NEX (#excitments)
Use half-fourier/ half scan

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22
Q

Changing the slice thickness directly affects what parameters?

A

The SNR, resolution, and the amount we can cover.

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23
Q

When increasing the number of exitations (NEX), this will ____ the SNR

Decrease or increase

A

decrease

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24
Q

When increasing NEX/NSA, SNR (signal-to-noise ratio) increases by the square root (√) of the
% increase

true or false?

A

True

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25
Q

If we have a sequence that 2 NEX, increased to 6 NEX (3times the total NEX)
would have an increase in SNR of √___?

A

√3, or 1.73 times more SNR than the original sequence.

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26
Q

When we increase the NEX, what other parameters are affected?

A

the scan time and SNR.

27
Q

If we increase the NEX, what happens to the resolution?

A

nothing

28
Q

NEX has NO EFFECT on pixel size

True or False

A

True

29
Q

When we use a smaller pixel size, this leads to ___ resolution but ____ SNR

A

Smaller pixel= Better resolution but worse SNR

30
Q

FOV, slice thickness and matrix are the parameters used to make adjustments to voxel volume

A

True

31
Q

What can happen when we have a long echo train length? (ETL)

A

this can make the image more blurry.

32
Q

FOV ÷ matrix is the formula used to calculate the size of a pixel.

A

True

33
Q

A gradient echo sequences lacks the 180 refocusing RF. True or False?

A

True. This makes it more susceptible to magnetic field inhomogeneities.

34
Q

Why are gradient echo sequences usually faster than the other sequences?

A

because they don’t have the 180 refocusing pulse, so the TR is shorter thus shortening the scan time.

35
Q

In a gradient echo pulse sequence, the gradient coils are used to refocus the
protons and create the echo

True or False

A

true

36
Q

Gradient echo sequences can yield either T1 or ___ characteristics by susceptibility, chemical shift, and inhomogeneities

T2 or T2*

A

T2*

37
Q

Reducing the FOV by a factor of 2 will reduce the voxel volume by a factor of ___

2, 4, 6? and why?

A

4

the FOV is measured in phase AND frequency dimensions, so when we reduce the FOV in HALF it’ll reduce the phase AND frequency dimensions EACH by 2 therefore the total reeduction is a factor of 4.

38
Q

What is rectangular FOV?

A

it shortens the overall FOV in the phase encoding direction reducing scan time while maintaining the resolution

39
Q

What is the scan time formula for a Spin Echo??

A

TR x Phase Matrix x NEX

40
Q

What is the scan time formula for FAST spin echo?

A

TR x Phase Matrix x NEX / ETL

similar to regular spin echo, but divided by ETL

41
Q

What is the scan time Formula for Gradient echo (2D)

A

TR x Phase Matrix x NEX

same as spin echo

42
Q

What is the scan time formula for Gradient Echo for 3D?

A

TR x Phase Matrix x NEX x # of slices.

43
Q

When we are doing these “scan time formulas” Remember to convert into seconds (divide the answer by 1000) and thatll be your answer but it in seconds. You’ll probably have to convert to minutes in your head.

A

Just remember that lol

44
Q

When moving blood enters a magnetic field, an effect on the ECG seen as the “__ - wave” swelling or spike occurs know as the magnetohydrodynamic effect

A

The T WAVE

45
Q

the FDA limits for the whole body SAR is ___ W/KG over 15 minutes.

A

4 watts / kg

46
Q

FDA limits for the head is ___ w/kg over 10 minutes

A

3 w/kg

47
Q

Regions of the body that do not quickly dissipate thermal absorption from SAR
during MR procedures are the ______ and ______

A

eyes and testicles

48
Q

The FDA limit on time varying magnetic fields is once
the patient experiences peripheral nerve stimulation.

True or False

A

True

49
Q

The general public is limited to a magnetic field of ___ Gauss

5, 10 or 50?

A

5 gauss

50
Q

Cables from local RF coils and gating leads should be braided and positioned
straight in the bore, NEVER in direct contact with the patient’s skin

True or False

A

True

51
Q

a patient may experience a visual stimulation known as

magnetophosphenes, what is this?

A

seeing stars

52
Q

RF energy is___ energy, ____
radiation

low energy or high?
non ionizing or ionizing

A

low energy, non ionizing

53
Q

The FDA regulates the acoustic noise.

True or False?

A

true

54
Q

What type of pulse sequence transmits the most RF to the patient and consequently can potentially have more SAR restrictions?

A

fast spin echo.

55
Q

the storage location of MR data is called?

A

k - space

56
Q

the total number of excess protons aligned with the magnetic field is the ____ magnetization vector

A

net magnetization vector

57
Q

the signal produced immediately after the RF pulse is called a ???

A

FID ( free induction decay)

58
Q

the outer lines of K-space contain??

resolution or signal/contrast?

A

resolution

59
Q

the central lines of k space contains?

high resolution or signal and contrast?

A

signal and contrast.

60
Q

2D acquistions usually require an interslice gap

True or False?

A

True

61
Q

3D sequences provide greater SNR and elimination of cross talk artifact.. True or False?

A

true

62
Q

What does MPR stand for and what is it?

A

Multi-planar reconstruction

it is an ability to generate images in scan planes as well as acquisition planes yieling multiple slice plan orientations from just one aquired data set.

63
Q

What is MIP and what does it stand for?

A

maximum intensity projection. a recon algorithm utilizing bright pixel intensities to create collapsed images of a data set. AKA MRAs

MRI QUIZ (10 decks)

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