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Ultrasound Physics > Artifacts > Flashcards

Artifacts Flashcards

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1
Q

Causes of Artifacts

A
  1. Violation of assumptions
  2. Equipment malfunction
  3. Natural physics of ultrasound
  4. Operator error
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2
Q

Hyperechoic

A

Parts of an image appear brighter than normal or surrounding tissue

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3
Q

Hypoechoic

A

Parts of an image that appear darker than normal or surrounding tissue

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4
Q

Anechoic

A

Without echoes, a severe form of hypoechoic

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5
Q

Isoechoic

A

Structures w/ equal echo brightness

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6
Q

Homogeneous

A

Parts of an image that have similar characteristics throughout

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7
Q

Heterogenous

A

Parts of an image that have differing characteristics throughout

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8
Q

Reverberation

A

Multiple, equally spaced echoes

→ Invalidates assumptions that echoes travel directly to a reflector and back

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9
Q

Characteristics od Reverberations

A
  1. Multiple, equally spaced
  2. Parallel to sound beam’s main axis
  3. Located at increasing depths
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10
Q

Comet Tail

A

aka ring down
Solid, hyperechoic line; occur when closely spaced reverberations merge
→ Invalidates assumptions that echoes travel directly to a reflector and back

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11
Q

Characteristics of Comet Tail

A
  1. Appear in areas w/ high prop. speed

2. Located parallel to the beam’s main axis

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12
Q

Shadow

A

Hypoechoic/anechoic region that extends below a highly attenuating structure
→ Invalidates assumption that the intensity of the reflector is related to the tissue causing the reflection

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13
Q

Edge Shadow

A

Special form of shadowing that appears at the edge of a curved reflector; caused by refraction from curve reducing intensity
→ Invalidates assumption that intensity of the reflector is related to the characteristics of the tissue causing the reflection

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14
Q

Enhancement

A

Hyperechoic region below tissues with very low attenuation
→ Invalidates assumption that intensity of the reflector is related to the characteristics of the tissue causing the reflection

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15
Q

Focal Enhancement

A

aka focal banding
Side-to-side region of image that is hyperechoic; strongly focused beam = brighter echoes
→ Invalidates assumption that intensity of the reflector is related to the characteristics of the tissue causing the reflection

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16
Q

Mirror Image

A

Replica of true reflector

→ Invalidates assumptions that sound travels in a straight line, and directly to a reflector and back

17
Q

Characteristics of Mirror Image

A
  1. Replica of true reflector (appears DEEPER than true reflector)
  2. Mirror (bright reflector) appears in between artifact & transducer
  3. True reflector & artifact are equal distances from mirror
18
Q

Crosstalk

A

Mirror image artifact for ONLY spectral Doppler; identical spectrum above and below the baseline
Occurs when gain is too high or incident angle is near 90 degrees

19
Q

Speed Error

A

aka range error artifact
Step-off; occurs when wave propagates at speed other than 1.54 km/s
→ Invalidates assumption that sound always travels at 1.54 km/s

20
Q

Slower Speed Error

A

Sound travels too slow and appears deeper; reported distance is too large

21
Q

Faster Speed Error

A

Sound travels too fast and appears closer; reported distance is too small

22
Q

Lobes

A

Appear when sound energy is transmitted in a direction other than the beam’s main axis
→ Invalidates assumption that reflections arise from structures located on beam’s main axis

23
Q

Characteristics of Lobes

A
  1. Located side by side to true reflector

2. True anatomy can be determined by using multiple views

24
Q

Side Lobes

A

Lobes created by a single crystal transducer

25
Q

Grating Lobes

A

Lobes created by multiple element (array) transducers; can be reduced w/ subdicing & apodization

26
Q

Refraction

A

Created when a sound pulse changes direction during transmission; side by side to reflector
→ Invalidates assumption that sound travels in a straight line

27
Q

Slice Thickness

A

Reflections from structures above/below imaging plane from dimension of beam perpendicular to imaging plane
→ Invalidates assumption that imaging plane is thin and uniform

28
Q

Characteristics of Slice Thickness

A
  1. Reduced w/ thinner imaging planes

2. Fills in hollow structures such as cysts

29
Q

Axial

A

Appearance of only 1 structure out of 2 that are laid in front of the other; appears if structures are closer than 1/2 SPL

30
Q

Lateral

A

Appearance of only 1 structure out of 2 that are side by side; occurs when reflectors are closer than the width of sound beam
Least likely to occur at focus

31
Q

Point Spread

A

Component of lateral resolution artifact; small reflector is displayed as a wide line rather than a narrow dot

32
Q

Multipath

A

Occurs when sound pulses bounce off a second structure on the way to or from the primary reflector

33
Q

Curved/Oblique

A

Reflection of sound away from transducer; results in reflectors being absent, weak, or appear different from surrounding structures

34
Q

Temporal

A

Poor frame rate results in inaccurate positioning of moving reflectors

35
Q

Spatial

A

Low line density results in less detail/poor resolution

36
Q

Range Ambiguity

A

Reflector is located deeper/shallower on image; eliminated by increasing PRP

37
Q

Noise

A

Small amplitude echoes resulting from electrical interference, signal processing, and fake reflectors

38
Q

Speckle

A

Noise resulting from constructive & destructive interference

39
Q

Clutter

A

Noise from false echoes located outside the main sound beam (i.e. side/grating lobes, section thickness)
In Doppler: contamination of accurate Doppler signals by vessel walls or heart muscles & their high amplitude reflections

Ultrasound Physics (11 decks)

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