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Stacy Final CH.6 > Ch. 6 Artifacts in scanning > Flashcards

Ch. 6 Artifacts in scanning Flashcards

1
Q

Improper Doppler-shift information from a pulsed wave Doppler or color Doppler instrument when the true Doppler shift exceeds one half the pulse repetition frequency

A

Aliasing

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2
Q

Echo-free

A

Anechoic

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3
Q

Movement of the zero Doppler-shift frequency or zero flow speed line up or down on a spectral display

A

Baseline shift

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4
Q

Series of closely spaced reverberation echoes

A

Comet tail

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5
Q

Leakage of strong signals in one direction channel of a Doppler receiver in the other channel; can produce the Doppler mirror-image artifact

A

Cross-talk

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6
Q

Increase in echo amplitude from reflectors that lie behind a weakly attenuating structure

A

Enhancement

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7
Q

Having relatively weak echoes

A

Hypoechoic

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8
Q

Artifactual gray-scale, color flow, of Doppler signal appearing on the opposite side (from the real structure or flow) of a strong reflector

A

Mirror image

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9
Q

Several reflections produced by a pulse encountering a pair of reflectors; reverberation

A

Multiple reflection

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10
Q

Doppler-shift frequency above which aliasing occurs; one half the pulse repetition frequency

A

Nyquist limit

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11
Q

Artifact produced when echoes are placed too close to the transducer because a second pulse was emitted before they were received

A

Range ambiguity

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12
Q

Condition where a driven mechanical vibration is of a frequency similar to a natural vibration frequency of the structure

A

Resonance

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13
Q

Multiple reflections

A

Reverberation

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14
Q

Artifact resulting from a continuous stream of sound emanating from an anatomic site

A

Ring-down

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15
Q

Thickness of the canned tissue volume perpendicular to the scan plane; also called slice thickness

A

Section thickness

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16
Q

Reduction in echo amplitude from reflectors that lie behind a strongly reflecting or attenuating structure

A

Shadowing

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17
Q

Granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in tissue

A

Speckle

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18
Q

Propagation speed that is different from the assumed value (1.54 mm/ms)

A

Speed error

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19
Q

Axial resolution

A

Caused by: Pulse length

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20
Q

Comet tail

A

Caused by: Reverberation

21
Q

Grating lobe

A

Caused by: Grating lobe

22
Q

Lateral resolution

A

Caused by: Pulse width

23
Q

Mirror image

A

Caused by: Multiple reflection

24
Q

Refraction

A

Caused by: Refraction

25
Q

Reverberation

A

Caused by: Multiple reflection

26
Q

Ring down

A

Caused by: Resonance

27
Q

Section thickness

A

Caused by: Pulse width

28
Q

Speckle

A

Caused by: Interference

29
Q

Speed error

A

Caused by: Speed error

30
Q

Range ambiguity

A

Caused by: High-pulse repetition frequency

31
Q

Shadowing

A

Caused by: High attenuation

32
Q

Edge shadowing

A

Caused by: Refraction or interference

33
Q

Enhancement

A

Caused by: Low attenuation

34
Q

Focal enhancement

A

Caused by: Focusing

35
Q

Aliasing

A

Caused by: Low-pulse repetition frequency

36
Q

Spectrum mirror

A

Caused by: High Doppler gain

37
Q

Artifacts in sonography occur as apparent structure that are one of the following

A
  1. Not real
  2. Missing
  3. Misplaced
  4. Of improper brightness, shape, or size
38
Q

Propagation Artifact do what?

A

Affects the beam as it travel through the body

39
Q

Name some Propagating Artifacts

A 
Section thickness
Speckle
Reverberation
Mirror image
Refraction
Grating lobes
Speed error
Range ambiguity
40
Q

Attenuation Artifacts do what?

A

Affects the beam as it reduces in amplitude

41
Q

Name some Attenuation Artifacts

A

Shadowing

Enhancement

42
Q

Spectral Doppler Artifacts are used to______________

A

Detect Doppler shifts

43
Q

Name some Spectral Doppler Artifacts

A 
Aliasing
Nyquist limit
Range ambiguity
Mirror image
Noise
44
Q

Color Doppler Artifacts are used to _________________________

A

Detect flow direction

45
Q

Name some Color Doppler Artifacts

A 
Aliasing
Mirror image
Shadowing
Clutter
Noise
46
Q

Focal banding can also be caused by:

A

Incorrect gain and TGC settings

47
Q

Methods of reducing or eliminating aliasing

A 
Shift the baseline*
Increase the pulse repetition frequency*
Increase the Doppler angle
Use a lower operating frequency
Use a continuous wave device

*These are the most convenient and commonly used methods. Both are required in extreme cases

48
Q

Aliasing is the most _________ artifact encountered in Doppler ultrasound

49
Q

Focal enhancement or focal banding

A

Brightening of echoes also can be caused by the increased intensity in the focal region of a beam because the beam is narrow there

Stacy Final CH.6 (4 decks)

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