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MRI Advanced applications Q > Artifacts > Flashcards

Artifacts Flashcards

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
Q

To correct for the artifact(white arrows) in Image 85:

A

Increase phase matrix

26
Q

Image 86 is an example of which kind of artifact?

A

Magnetic susceptibility

27
Q

Image 87 displays what kind of artifact?

A

Motion/ghosting in the phase direction

28
Q

Image 88 displays what kind of artifact?

A

RF zipper

29
Q

Image 89 displays what kind of artifact?

A

Wraparound (aliasing)

30
Q

To correct for the artifact in Image 89

A

Utilize oversampling

Enable anti-aliasing option

31
Q

Image 90 (white arrow) displays what kind of artifact?

A

Wraparound (aliasing)

32
Q

To correct for the artifact in Image 90:

A

Increase FOV

33
Q

When the TE is lowered:

A

Susceptibility artifact decreases

34
Q

The arrows in Image 100 are pointing to which kind of artifact?

A

Cross talk artifact

35
Q

The artifact in Image 100 is caused by:

A

The imperfect shape of RF slice profiles, which leads to an unintended excitation of an adjacent slice or tissue

36
Q

One can correct for the artifact seen in Image 100 by:

A

Increasing interslice gap
Interleaved slice order
Acquiring stacks as complete packages

37
Q

Letter A in Image 101 is pointing to what type of MR artifact?

A

Chemical shift

38
Q

The artifact in Image 101 is caused by:

A

Differing frequencies of fat and water

39
Q

To reduce an RF zipper artifact:

A

Close scan room door and ensure adequate door suction

40
Q

Ensuring adequate door suction in the MR scan room will aid in preventing which artifacts from appearing in an MR image?

A

RF zipper

41
Q

The arrows in Image 99 are pointing to what kind of artifact?

A

Moire

42
Q

The artifact in Image 99 is caused by

A

Interference of aliased signals at different phases

43
Q

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.

A

4 Tesla; 8 Tesla

44
Q

To correct for the artifact shown in Image 172, the MRI technologist would

A

larger Field of View

reduced parallel imaging reduction factor

45
Q

The red arrows in Image 172 are indicative of which type of MRI artifact?

A

Parallel Imaging

46
Q

To correct for the artifact shown in Image 173, the MRI Technologist would:

A

increase in NSA/NEX

enabling Flow Compensation

47
Q

The artifact identified by the orange arrows in Image 173 is a _____________ artifact.

A

FID crushing/ fine line

48
Q

____________ techniques should be avoided in metal artifact reduction sequences, as they require a gradient echo-based coil calibration sequence prior to implementation.

A

Parallel imaging

49
Q

Magnetic resonance imaging (MRI) uses ________ separate magnetic fields to perform the task of routine image acquisition.

A

three

50
Q

What is the term used to measure the magnetic field strength in the periphery of the MRI scan room?

A

Gauss

51
Q

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.

A

main static

52
Q

What is the term used to describe gradient field interactions as visual light flashes, or “seeing stars”?

A

magnetophosphenes

53
Q

Which gradient is primarily responsible for performing the function of determining slice thickness, scan plane and orientation of a pulse sequence?

A

slice select gradient

54
Q

All of the following are potential risk factors for SAR thermal absorption during an MR pulse sequence EXCEPT:

A

Hypotension

55
Q

______________ are caused by local eddy currents due to the increased conductivity of body tissue, and are identified by areas of shading or signal loss.

A

Dielectric effects

56
Q

The yellow arrows in Image 201 display what type of MRI artifact?

A

Dielectric effects

57
Q

The yellow arrows in Image 202 are pointing to which artifact

A

magic angle

58
Q

The yellow arrows in Image 203 identify what artifact?

A

Annefact

59
Q

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.

A

Annefact

60
Q

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

A

Magic angle

MRI Advanced applications Q (3 decks)

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