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MRI in practice 5th ed. > Chapter 7 > Flashcards

Chapter 7 Flashcards

Protocol optimization

1
Q

Optimization of image quality in MRI generally represents a compromise between:

a. Image contrast, SNR and acquisition time
b. Height, width and depth of the voxel
c. Patient age and time of day
d. None of the above

A

a. Image contrast, SNR and acquisition time

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2
Q

In most instances, when spatial resolution is increased, signal to noise is:

a. Increased
b. Decreased
c. Unchanged
d. Doubled

A

b. Decreased

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3
Q

The ______ controls the amount of data stored in each line of K-space.

a. NMV
b. NTC
c. NEX
d. SNR

A

c. NEX

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4
Q

Voxel volume is determined by

a. FOV
b. Slice Thickness
c. Matrix
d. All of the above

A

d. All of the above

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5
Q

As the voxel size increases the SNR ________________

a. Increases
b. Decreases
c. Stays the same
d. Doubles

A

a. Increases

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6
Q

In most cases, to demonstrate anatomy, high SNR ____ are selected

a. TI weighted images
b. T2 weighted images
c. Inversion recovery
d. Gradient echo

A

a. TI weighted images

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7
Q

Increasing only the TE allows for _______ slices

a. More
b. Less
c. No change
d. None of the above

A

b. Less

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8
Q

If the slice thickness doubles, SNR _____________

a. Increases
b. Decreases
c. Stays the same
d. Doubles

A

d. Doubles

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9
Q

To double the SNR we need to increase the NEX and the scan time by a factor of:

a. three
b. four
c. two
d. five

A

b. four

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10
Q

In large voxels, individual signal intensities are averaged together and not represented as distinct within the voxel. This results in:

a. partial voluming
b. black space
c. white space
d. no image detail

A

a. partial voluming

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11
Q

To obtain good resolution, achieving thin slices requires the slice select gradient slope to be:

a. horizontal
b. gradual
c. steep
d. vertical

A

c. steep

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12
Q

A coarse matrix is one with a low number of frequency encodings and/or phase encodings.

a. True
b. False

A

a. True

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13
Q

Which of the following is the correct scan time for a spin echo sequence with the following parameters: TR 220msec, TE 20msec, Matrix 512 x 512, NEX 3, FOV 230mm

a. 5 min 6 sec
b. 5 min 38 sec
c. 9 min 23 sec
d. 10 min 38 sec

A

b. 5 min 38 sec

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14
Q

The approximate scan time of a fast spin echo sequence with a TR of 3500msec, TE 90msec, matrix 256 x 256, NEX 1, FOV 220mm and an ETL of 5 is ____ minutes?

a. 3
b. 8
c. 11
d. 15

A

a. 3

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15
Q

When increasing the matrix, the pixel size will:

a. Increase
b. Stay the same
c. Decrease
d. Vary

A

c. Decrease

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16
Q

In order to produce a high quality reformatted image, the:

a. Acquisition voxel should be as rectangular as possible
b. Patient must hold their breath for the entire scan
c. Acquisition voxel should be isotropic
d. Acquisition voxel should be anisotropic

A

c. Acquisition voxel should be isotropic

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17
Q

Increasing the NEX:

a. has no effect on reducing motion artifacts
b. increases the SNR
c. motion artefact is averaged out of the image
d. b and c

A

d. b and c

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18
Q

For the following spin echo protocol: FOV: 320mm, TR 500msec, TE 25msec, Slice thickness 5mm, slice gap 9mm, NEX 4, Matrix 192; increasing the TE will:

a. Decrease the SNR and decrease slice number
b. Increase the SNR and increase slice number
c. Increase scan time
d. Decrease scan time

A

a. Decrease the SNR and decrease slice number

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19
Q

If the matrix size increases and the FOV remains the same:

a. Pixel size decreases
b. Frequency encoding decreases
c. Slice thickness is changed
d. Voxel size increases

A

a. Pixel size decreases

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20
Q

For the following spin echo protocol: FOV 320msec, TR 500msec, TE 25msec, Slice thickness 5mm, Gap 1mm, Number of slices 9, NEX 4, Matrix 192 x 192. Increasing the FOV, TR and slice gap will

a. Increase the scan time
b. Decrease the scan time
c. Not affect the scan time

A

a. Increase the scan time

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21
Q

Which of the following would result from increasing the number of signal averages?

a. Increased SNR
b. Increased scan time
c. None of these
d. A and B

A

d. A and B

22
Q

“The ability to differentiate small differences in signal intensity between adjacent tissues” is a definition of?

a. Spatial resolution
b. Magnetization transfer
c. Partial volume averaging
d. Contrast resolution

A

d. Contrast resolution

23
Q

The brightness of the pixel represents the strength of the MRI signal generated by a unit volume of patient tissue called a:

a. Cuboid
b. Voxel
c. Matrix
d. Slice

24
Q

All other factors being equal, if the FOV is increased:

a. Matrix size is increased
b. Contrast is increased
c. Pixel size is increased
d. SNR is decreased

A

c. Pixel size is increased

25
Q

Which of the following will reduce partial volume artifact?

a. Decreasing slice gap
b. Reducing slice thickness
c. Increasing echo time
d. Increasing the FOV

A

b. Reducing slice thickness

26
Q

Which image parameter directly affects scan time?

a. TR
b. TE
c. TI
d. TAU

27
Q

Which of the following parameters would NOT improve SNR?

a. Decreasing the FOV
b. Increasing the slice thickness
c. Increasing the TR
d. Decreasing the bandwidth

A

a. Decreasing the FOV

28
Q

To reduce the scan time:

a. Reduce the TE
b. Increase the number of phase encodings
c. Decrease the NEX
d. Increase the TR

A

c. Decrease the NEX

29
Q

All other factors being equal, if the TR is increased:

a. FOV is decreased
b. SNR is increased
c. T1 weighting is increased
d. Number of phase encodings is decreased

A

b. SNR is increased

30
Q

Which of the following would produce the strongest SNR:

a. Gradient pulse sequence
b. Spin-echo pulse sequence
c. A saturation band
d. 45 degree flip angle

A

b. Spin-echo pulse sequence

31
Q

A long TR ___________ SNR.

a. Increases
b. Slightly decreases
c. Decreases (by a factor of 4)
d. Has no effect on

A

a. Increases

32
Q

A short TE ___________ SNR.

a. Has no effect on
b. Slightly decreases
c. Decreases (by a factor of 4)
d. Increases

A

d. Increases

33
Q

To improve spatial resolution:

a. Increase FOV
b. Increase the number of phase encodings
c. Increase slice thickness
d. Increase the number of signal averages

A

b. Increase the number of phase encodings

34
Q

If you minimize scan time by reducing the TR, which would NOT be a result?

a. Increased T1 weighting
b. Reduced SNR
c. Increased number of phase encodings
d. Reduced number of slices

A

c. Increased number of phase encodings

35
Q

A decrease in receive bandwidth:

a. Increases spatial resolution
b. Increases SNR
c. Increases contrast resolution
d. Decreases scan time

A

b. Increases SNR

36
Q

All other factors being equal, if the matrix is increased:

a. Pixel size is increased
b. Contrast resolution is reduced
c. SNR is increased
d. Spatial resolution is increased

A

d. Spatial resolution is increased

37
Q

What is the main disadvantage of volume scanning?

a. Reduced SNR
b. Reduced CNR
c. Increased scan times
d. Reduced spatial resolution

A

c. Increased scan times

38
Q

Isotropic voxels:

a. Increase SNR
b. Give equal resolution in every plane
c. Increase NEX
d. Decrease scan time

A

b. Give equal resolution in every plane

39
Q

For the following spin echo protocol: FOV 320 msec, TR 500msec, TE 25msec, Slice thickness 5mm, Gap 1mm, Number of slices 9, NEX 4, Matrix 192 x 192. Increasing NEX will:

a. Increase SNR and signal averaging
b. Decrease SNR and signal averaging
c. Decrease the scan time
d. Not affect the scan time

A

a. Increase SNR and signal averaging

40
Q

All other factors being equal, if the slice thickness is increased, the spatial resolution:

a. Increases
b. Decreases
c. Stays the same
d. Is not affected

A

b. Decreases

41
Q

Changing the size of the voxel in the frequency direction will:

a. Double the scan time
b. Decrease the scan time
c. Have no effect on the scan time
d. Increase the scan time by a factor of 357

A

c. Have no effect on the scan time

42
Q

Factors that affect spatial resolution include all of the following EXCEPT:

a. FOV
b. Flip angle
c. Matrix
d. Slice thickness

A

b. Flip angle

43
Q

Factors that affect SNR include all of the following EXCEPT:

a. TR
b. Field strength
c. FOV
d. Scan time

A

d. Scan time

44
Q

Calculate the pixel area for the following sequence: TR 4000, TE 120, FOV 28cm, 304 x 304 matrix, 2 NEX, ETL 12

a. 0.76 mm2
b. 0.85 mm2
c. 0.92 mm2
d. 1.84 mm2

A

b. 0.85 mm2

45
Q

Scan time can be determined using which three parameters?

a. Frequency matrix, TE, NEX
b. Phase matrix, TE, NEX
c. Phase matrix, TR, NEX
d. Frequency matrix, TR, NEX

A

c. Phase matrix, TR, NEX

46
Q

At 1.5T the chemical shift between fat and water is:

a. 147Hz
b. 440Hz
c. 220HZ
d. 660Hz

47
Q

Which of the following is NOT part of spatial inversion recovery (SPIR)?

a. TI corresponding to null point of fat
b. 180 degree pre-saturation pulse
c. more affected by inhomogeneity than STIR
d. fat is not selectively nulled

A

d. fat is not selectively nulled

48
Q

Comparing SPIR to STIR:

a. in STIR fat is uniformly suppressed
b. you can use Gd with SPIR
c. SPIR images are not suppressed uniformly due to field inhomogeneities
d. all of the above are correct

A

d. all of the above are correct

49
Q

Reducing the TE yields images with:

a. More T1 information
b. Less T1 information
c. More T2 information
d. Less T2 information

A

d. Less T2 information

50
Q

Reducing the flip angle yields images with:

a. More T1 information
b. Less T1 information
c. More T2 information
d. Less T2 information

A

b. Less T1 information

51
Q

What would the Scan time be for this 3D volume acquisition: TR 32ms, TE 4ms, FOV 18cm, 2mm slice thickness, 96 slices, 192 x 256 matrix, 1 NEX, Flip angle 15°

a. 4 min 28 sec
b. 5 min 12 sec
c. 8 min 42 sec
d. 9 min 50 sec

A

d. 9 min 50 sec

MRI in practice 5th ed. (10 decks)

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