Artifacts Flashcards

(60 cards)

1
Q

DWI susceptibility artifacts in or around strong air tissue interfaces can be minimized by:

A

Increasing parallel imaging acceleration factor

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2
Q

All of the following artifacts except __________ occur along the phase encoding axis.

A

Chemical Shift

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3
Q

Motion is seen as a smearing across the image in the:

A

phase encoding direction

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4
Q

Magnetic susceptibility artifacts are more prominent with:

A

Gradient echo

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5
Q

A leak in the RF shielding can appear as

A

A zipper artifact in the frequency direction

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6
Q

A remedy for a Gibbs truncation artifact would be

A

Increase the number of phase encodings

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7
Q

A FID crushing artifact can be eliminated with the use of:

A

Increase in NEX and/or enabling Flow Compensation

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8
Q

Chemical shift artifact occurs because:

A

Fat and water precess at different frequencies

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9
Q

he ___________ to reduce chemical shift artifacts

A

Receiver bandwidth should be increased

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10
Q

Aliasing occurs because tissue outside the selected FOV is:

A

Undersampled

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11
Q

The ________ should be _______ to reduce chemical shift artifacts

A

Receiver bandwidth; increased

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12
Q

Which artifact mimics a syrinx in the spine?

A

Truncation

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13
Q

________ occurs when tissue outside the Field of View is undersampled, causing a misregistration of anatomical location, in the phase direction, but on the opposite side of the anatomical location, also known as wrap-around artifact.

A

Aliasing artifact

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14
Q

In what anatomical region would you expect to see chemical misregistration the least?

A

Cerebellum

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15
Q

Which artifact occurs because of chemical misregistration?

A

Chemical shift

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16
Q

Which of the following influences can lead to artifacts?

A

Magnetic field inhomogeneity,

machine hardware,

the patient

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17
Q

In a sagittal cervical spine MRI, what could be done to compensate for CSF flow artifacts?

A

Enable gradient moment nulling

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18
Q

Which would yield more chemical shift artifacts?

A

3T superconducting magnet

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19
Q

Which of the following could lead to poor fat suppression?

A

Inhomogeneity

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20
Q

A decrease in the voxel volume yields:

A

A decrease in partial volume averaging

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21
Q

To reduce the appearance of a Gibbs truncation artifact, the

A

Number of phase encodings must be increased

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22
Q

To minimize cross talk artifact

A

Increase the interslice gap

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23
Q

Image 84 displays what type of artifact

A

Magnetic susceptibility

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24
Q

he arrows in Image 85 point to what kind of artifact?

A

Gibbs truncation

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25
To correct for the artifact(white arrows) in Image 85:
Increase phase matrix
26
Image 86 is an example of which kind of artifact?
Magnetic susceptibility
27
Image 87 displays what kind of artifact?
Motion/ghosting in the phase direction
28
Image 88 displays what kind of artifact?
RF zipper
29
Image 89 displays what kind of artifact?
Wraparound (aliasing)
30
To correct for the artifact in Image 89
Utilize oversampling Enable anti-aliasing option
31
Image 90 (white arrow) displays what kind of artifact?
Wraparound (aliasing)
32
To correct for the artifact in Image 90:
Increase FOV
33
When the TE is lowered:
Susceptibility artifact decreases
34
The arrows in Image 100 are pointing to which kind of artifact?
Cross talk artifact
35
The artifact in Image 100 is caused by:
The imperfect shape of RF slice profiles, which leads to an unintended excitation of an adjacent slice or tissue
36
One can correct for the artifact seen in Image 100 by:
Increasing interslice gap Interleaved slice order Acquiring stacks as complete packages
37
Letter A in Image 101 is pointing to what type of MR artifact?
Chemical shift
38
The artifact in Image 101 is caused by:
Differing frequencies of fat and water
39
To reduce an RF zipper artifact:
Close scan room door and ensure adequate door suction
40
Ensuring adequate door suction in the MR scan room will aid in preventing which artifacts from appearing in an MR image?
RF zipper
41
The arrows in Image 99 are pointing to what kind of artifact?
Moire
42
The artifact in Image 99 is caused by
Interference of aliased signals at different phases
43
The Food and Drug Administration (FDA) set static magnetic field clinical use limits of _________ for the entire population and __________ for those over 1 month of age.
4 Tesla; 8 Tesla
44
To correct for the artifact shown in Image 172, the MRI technologist would
larger Field of View reduced parallel imaging reduction factor
45
The red arrows in Image 172 are indicative of which type of MRI artifact?
Parallel Imaging
46
To correct for the artifact shown in Image 173, the MRI Technologist would:
increase in NSA/NEX enabling Flow Compensation
47
The artifact identified by the orange arrows in Image 173 is a _____________ artifact.
FID crushing/ fine line
48
\_\_\_\_\_\_\_\_\_\_\_\_ techniques should be avoided in metal artifact reduction sequences, as they require a gradient echo-based coil calibration sequence prior to implementation.
Parallel imaging
49
Magnetic resonance imaging (MRI) uses ________ separate magnetic fields to perform the task of routine image acquisition.
three
50
What is the term used to measure the magnetic field strength in the periphery of the MRI scan room?
Gauss
51
The __________ magnetic field poses risks to patients and staff, due to the torpedo effect when a ferromagnetic object becomes magnetized and attracts to the large magnet.
main static
52
What is the term used to describe gradient field interactions as visual light flashes, or "seeing stars"?
magnetophosphenes
53
Which gradient is primarily responsible for performing the function of determining slice thickness, scan plane and orientation of a pulse sequence?
slice select gradient
54
All of the following are potential risk factors for SAR thermal absorption during an MR pulse sequence EXCEPT:
Hypotension
55
\_\_\_\_\_\_\_\_\_\_\_\_\_\_ are caused by local eddy currents due to the increased conductivity of body tissue, and are identified by areas of shading or signal loss.
Dielectric effects
56
The yellow arrows in Image 201 display what type of MRI artifact?
Dielectric effects
57
The yellow arrows in Image 202 are pointing to which artifact
magic angle
58
The yellow arrows in Image 203 identify what artifact?
Annefact
59
Primarily stemming from active RF coil channels or elements outside the scanning field of view, ______________ artifacts can be corrected by simply de-selecting the element(s) outside the scanning range.
Annefact
60
A _____________ artifact occurs when a tendon or ligament is positioned approximately 55° to the direction of the main magnetic field, and a short TE value pulse sequence is utilized
Magic angle