image formation

Question 1

Which of the following statements is FALSE regarding the use of a narrow receiver bandwidth?

A. It generates lower signal-to-noise ratio images
B. It should be applied in anatomical regions that contain high fat and water interfaces
C. It is utilized with a high readout gradient amplitude
D. All of the above

Answer 1

All of the above

Question 2

: A ______________ is defined as a picture element and has _________ characteristics.

Answer 2

Pixel, two-dimensional

Question 3

The maximum intensity projection algorithm

Answer 3

Projects the high intensity pixels which represent blood vessels/ducts into one image

Question 4

Two gradients applied at the same time during slice selection are utilized for

Answer 4

Encoding oblique slice planes

Question 5

The readout gradient is usually turned on during the sampling or readout of the peak echo and also during which other process?

Answer 5

Frequency encoding

Question 6

If the maximum slices in a set TR is 10, and the necessary number of slices for a given sequence’s anatomical coverage is 26, how many acquisitions (packages) will be required

Answer 6

3

Question 7

Slice ___________ is determined by the slice selection process.

A. Position
B. Orientation
C. Thickness
D. All of the above

Answer 7

All of the above

Question 8

What effect would decreasing the FOV have on the spatial resolution of an image

Answer 8

Increase

Question 9

What effect would using a steep slice select slope and/or narrow bandwidth have on slice thickness?

Answer 9

Slices will be thin

Question 10

Which set of scan parameters below would yield the best spatial resolution?

A. 270 mm FOV, 192 x 512 matrix, 5mm slice thickness, 8 NEX
B. 270 mm FOV, 256 x 512 matrix, 5mm slice thickness, 4 NEX
C. 200 mm FOV, 512 x 512 matrix, 3mm slice thickness, 4 NEX
D. 200 mm FOV, 512 x 512 matrix, 5mm slice thickness, 4 NEX

Answer 10

200 mm FOV, 512 x 512 matrix, 3mm slice thickness, 4 NEX

Question 11

An isotropic voxel refers to a __________ shaped voxel.

Answer 11

Cubic

Question 12

: If the radiologist requires 3mm slices axially acquired through the IAC, with a slice gap of 0.5mm, and requires 4.2cm total coverage, how many slices must be selected?

Answer 12

12

Anatomic slice coverage: Slice thickness + interslice gap x # of slices

Question 13

If 24 4mm slices are planned with a gap of 1mm, the total anatomic coverage is _______ cm.

Answer 13

12
24 slices x 5mm (4 thickness + 1 gap) = 120 mm; ÷ 10 to calculate the coverage in cm.

Question 14

Which of the following is NOT a result of reducing the FOV?

Answer 14

Anatomical structures are displayed smaller in the image

Question 15

Creating additional images in various planes from a 3D data set is accomplished by a technique known as:

Answer 15

Multi-Planar reconstruction (MPR

Question 16

Which of the following can be considered an advantage of selecting a 3D acquisition as opposed to a 2D acquisition?

A. The slices have a greater SNR

B. No crosstalk

C. Longer repetition times

D. All of the above

E. A & B only

Answer 16

A & B only

Question 17

Multiplanar reconstructions are typically utilized in 3D pulse sequences because

A. 2D slices are too thick to reformat
B. 2D slice groups are too long
C. There are gaps between 2D slices
D. A & C only
E. B & C only

Answer 17

A & C only

Question 18

The process that digitizes the MR signals is known as

Answer 18

Fourier transform

Question 19

The signal produced immediately following an RF pulse is:

Answer 19

FID

Question 20

__________ is defined as a small change in the magnetic field along a particular axis

Answer 20

A gradient

Question 21

_________ is a file on the computer where the collected echoes are stored prior to being processed into an image by the Fourier Transform

Answer 21

Raw data

Question 22

In order to generate an MR image, the slice select gradient must be turned on during

Answer 22

RF energy application

Question 23

Decreasing the slice selection gradient strength will ________ of the resulting slice

Answer 23

Change the slice thickness

Question 24

The range of transmitted frequencies at each slice position must _____ to maintain slice thickness.

Answer 24

Remain constant

Question 25

All of the following are true mechanisms of saturation EXCEPT

Answer 25

Partial saturation yields T1 weighting; occurs when NMV is 180°

Question 26

Applying two gradients simultaneously during slice selection would

Answer 26

Produce an oblique slice

Question 27

A narrow receiver bandwidth:

Answer 27

Increases susceptibility artifact

Question 28

Which factors affect the flip angle?

Answer 28

Strength and duration of the RF field

Question 29

: To increase the voxel volume, which parameters would be adjusted

Answer 29

FOV, slice thickness and matrix

Question 30

Signal to Noise Ratio (SNR) would increase in a 3D volume acquisition with an increase in: A. TE B. Slices C. Field of view D. All of the above E. B and/or C only

Answer 30

B and/or C only

Question 31

A technique that reduces scan time by not filling as many lines of k-space in the phase direction, while maintaining spatial resolution, is known as:

Answer 31

Rectangular FOV

Question 32

To obtain a thin slice thickness

Answer 32

A steep gradient is applied with the transmit bandwidth at the Larmor frequency of H

Question 33

The Ernst angle can be defined as the optimal ___________ that yields the ____________ signal for a particular spin in the least amount of time.

Answer 33

Flip angle; maximum

Question 34

As the flip angle is increased, SNR(signal to noise ratio):

Answer 34

Increases to a point called the Ernst angle

Question 35

When gradient moment nulling is used as an imaging option in MR sequences

Answer 35

The minimum TE is increased

Question 36

Gradient moment nulling is used to compensate for: I. First order motion II. Second order motion III. Slow flowing vessels IV. Fast flowing vessels

Answer 36

I and III

Question 37

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

Answer 37

I and II

Question 38

Increasing the field of view (FOV) would have what effect?

Answer 38

Decrease spatial resolution

Question 39

2D acquisitions usually require

Answer 39

An interslice gap

Question 40

In a gradient echo sequence, reducing the flip angle while maintaining the TR reduces

Answer 40

Saturation

Question 41

Reducing the TE

Answer 41

Decreases the contrast based on T2 tissue relaxation times

Question 42

Reducing the TR: A. Increases the SNR of the image B. Decreases the SNR of the image C. Decreases the contrast based on the T2 relaxation time D. Increases saturation effects E. A and D only F. B and D only G. B, C and D only

Answer 42

B and D only

Question 43

Increasing the TE: A. Increases the contrast based on T1 tissue relaxation times B. Decreases the SNR of the image C. Decreases the contrast based on T2 tissue relaxation times D. Increases the contrast based on T2 relaxation times E. A and B only F. B and C only G. B and D only

Answer 43

B and D only

Question 44

Complete saturation is a condition where

Answer 44

: Longitudinal magnetization is not allowed to recover between excitations

Question 45

Gradient echo sequences use flip angles

Answer 45

To control saturation effects

Question 46

The presaturation pulses typically are found A. Between the 90º and the 180º pulses B. Prior to the TE C. Following the 180º pulse D. Prior to the excitation pulse E. A and D only

Answer 46

Prior to the excitation pulse

Question 47

Presaturation pulses are often used to:

Answer 47

Reduce flow artifacts

Question 48

Decreasing rBW (receiver bandwidth)by a factor of two:

Answer 48

Increases SNR by √2

Question 49

Decreasing the receiver bandwidth (utilizing a narrow BW): A. Increases the number of slices available B. Decreases the number of slices available C. Does not change the number of slices available D. Decreases SNR E. A and D only F. B and D only

Answer 49

Decreases the number of slices available

Question 50

Decreasing the receiver bandwidth (utilizing a narrow BW): A. Increases susceptibility artifact B. Decreases susceptibility artifact C. Does not affect susceptibility artifact D. Decreases SNR E. A and D only F. B and D only

Answer 50

Increases susceptibility artifact

Question 51

Decreasing the receiver bandwidth (utilizing a narrow BW): A. Reduces readout time B. Increases readout time C. Does not affect the readout time D. Increases SNR E. A and D only F. B and D only

Answer 51

B and D only

Question 52

Decreasing the receiver bandwidth (narrow rBW): A. Increases the contrast based on T1 tissue relaxation times B. Decreases the SNR of the image C. Increases the SNR of the image D. Inverts the SNR of the image E. Does not affect the SNR of the image

Answer 52

Increases the SNR of the image

Question 53

The time during which the frequency encoding gradient is on

Answer 53

Increases with a reduction in receiver bandwidth

Question 54

: If the receiver bandwidth (rBW) is decreased, the sampling rate

Answer 54

Decreases

Question 55

Increasing the receiver bandwidth (rBW):

Answer 55

Decreases chemical shift artifacts