220 Imaging > Part D: Artifacts > Flashcards

Part D: Artifacts Flashcards

(24 cards)

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1
Q
  1. The superimposition of signal that occurs when a LARGE FOV is acquired is known as:
    a. Wrap around
    b. Fold over
    c. Aliasing
    d. Partial volume averaging
A

d. Partial volume averaging

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2
Q
  1. The superimposition that occurs when a SMALL FOV is acquired is known as all of the following EXCEPT:
    a. Wrap around
    b. Fold over
    c. Aliasing
    d. Partial volume averaging
A

d. Partial volume averaging

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3
Q
  1. Motion is seen as a smearing in the:
    a. Frequency-encoding direction
    b. Phase-encoding direction
    c. Slice-selection direction
    d. a axis direction
A

b. Phase-encoding direction

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4
Q
  1. Aliasing occurs because tissue outside the selected FOV is:
    a. Undersampled
    b. Oversampled
    c. Not sampled
    d. Too large
A

a. Undersampled

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5
Q
  1. In order to compensate for aliasing:
    a. The scan can be shortened
    b. The FOV can be enlarged
    c. An oversampling technique can be employed
    d. b and c
A

d. b and c

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6
Q
  1. Gibbs, or truncation, artifact is seen as:
    a. Tissue that looks very similar to aliased tissue
    b. A bright pixel in the center of the image
    c. Dark lines between fat and water interfaces within the image
    d. High and low signal intensity bands
A

d. High and low signal intensity bands

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7
Q
  1. To correct for Gibbs artifact the:
    a. Number of phase encodings is decreased
    b. Number of phase encodings is increased
    c. FOV is increased
    d. TE is decreased
A

b. Number of phase encodings is increased

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8
Q
  1. Chemical shift occurs because the:
    a. System is undersampling the fat and water molecules
    b. SNR is low
    c. Fat and water precess at different frequencies
    d. Tissue is undersampled in the frequency direction
A

c. Fat and water precess at different frequencies

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9
Q
  1. Chemical shift becomes more obvious as the:
    a. Transmitter bandwidth is increased
    b. Receiver bandwidth is decreased
    c. Receiver bandwidth is increased
    d. Field strength of the magnet decreases
A

b. Receiver bandwidth is decreased

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10
Q
  1. Magnetic susceptibility effects are more prominent with:
    a. Gradient echo sequences
    b. Spin echo sequences
    c. Fast spin echo sequences
    d. Inversion recovery sequences
A

a. Gradient echo sequences

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11
Q
  1. Magnetic susceptibility effects are less prominant with:
    a. Gradient echo sequences
    b. Spin echo sequences
    c. Fast spin echo sequences
    d. Inversion recovery sequences
A

c. Fast spin echo sequences

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12
Q
  1. Susceptibility effects can be reduced by:
    a. Reducing the FOV
    b. Reducing the TR
    c. Reducing the TE
    d. a and c
A

d. a and c

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13
Q
  1. A leak in the RF shielding can appear as a:
    a. Bright spot in the center of the image
    b. ‘Zipper’ artifact in the frequency direction
    c. Wet spot on the image
    d. Ghost along the image’s edge
A

b. ‘Zipper’ artifact in the frequency direction

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14
Q
  1. Flow artifacts can be reduced by:
    a. Gradient moment nulling
    b. Spatial presaturation pulses
    c. Shortening the TE
    d. All of the above
A

d. All of the above

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15
Q
  1. A decrease in voxel volume leads to a decrease in:
    a. Chemical shift
    b. Aliasing
    c. Partial volume averaging
    d. a and c
A

d. a and c

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16
Q
  1. As FOV increases, partial volume averaging:
    a. Increases
    b. Decreases
    c. Stays the same
    d. Is not affected
17
Q
  1. As slice thickness increases, partial volume averaging:
    a. Increases
    b. Decreases
    c. Stays the same
    d. Is not affected
18
Q
  1. As matrix increases, partial volume averaging:
    a. Increases
    b. Decreases
    c. Stays the same
    d. Is not affected
19
Q
  1. As TR increases, partial volume averaging:
    a. Increases
    b. Decreases
    c. Stays the same
    d. Is not affected
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A

d. Is not affected

20
Q
  1. Respiratory artifacts can be reduced by:
    a. Respiratory gating
    b. Respiratory triggering
    c. Increasing the number of signals averaged
    d. All of the above
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A

d. All of the above

21
Q
  1. Motion artifact occurs due to period and/or aperiodic motion, whereby respiratory motion s an example of:
    a. Periodic motion
    b. Aperiodic motion
    c. Random motion
    d. Daily
Study These Flashcards
A

a. Periodic motion

22
Q
  1. Motion artifact occurs due to period and/or aperiodic motion, whereby patient movement is an example of:
    a. Periodic motion
    b. Aperiodic motion
    c. Random motion
    d. Daily
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A

a. Periodic motion

23
Q
  1. Motion artifact occurs due to period and/ or aperiodic motion, whereby patient movement is an example of:
    a. Periodic motion
    b. Aperiodic motion
    c. Pulsatile motion
    d. Daily
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A

b. Aperiodic motion

24
Q
  1. Motion artifact occurs due to period and/ or aperiodic motion, whereby peristaltic motion is an example of:
    a. Periodic motion
    b. Aperiodic motion
    c. Pulsatile motion
    d. Daily
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A

b. Aperiodic motion

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