Artifacts

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created 6 years ago by Annabelle
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sonography
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Cause

Comet Trails

Sound wave between two very closely spaced reflectors that merge and generate a series of closely spaced, discrete echoes

•Usually caused by small calcifications and metal objects like surgical pin
•Could also arise from the vibration of small highly reflective surfaces such as air bubbles
•This happens more often when the reflectors are located in a medium with high propagation speed.

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Description

Comet Trails

•appears distal to the highly reflective structure as a single solid hyperechoic (bright white) “tail” and is parallel to the sound beams main axis

•the complexity of the pattern depends on size, shape, and composition of the reflector, also the scan orientation and distance from the transducer

•usually in otherwise echo free areas on the image

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Benefit

Comet Trails

•used in ruling out pneumothorax

•If a pneumothorax is present, air within the pleural space hinders the propagation of ultrasound waves, thereby preventing the formation of comet tail artifacts

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Problems

Comet Trails

•significant loss of energy so the sound is not able to reach a far depth

•not able to view underneath reflector because of tail

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Assumptions

Comet Trail

1. Sound travels in a straight line.
2. Sound travels directly to a reflector and back

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Cause

Reverberation

•Caused by bouncing back and forth of the sound wave between two strong reflectors that are parallel to the ultrasound beam

•Reflections “ping pong” between structure and transducer

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Description

Reverberation

•Resembles a ladder or venetian blind

•Multiple, equally spaced echoes

•Located at ever increasing depths, each echo is deeper than the next

•1st and 2nd reflections closest to transducer are real, the multiple reflections displayed beneath the real reflector are artifacts

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Assumption

Reverberation

1. Sound travels in a straight line.
2. Sound travels directly to a reflector and back

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Cause

Ring Down

created from the vibrations of fluid trapped within air bubbles

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Description

Ring Down

•Appear as hyperechoic (bright white) parallel bands that reach to the bottom of the image and represent the continuous ringing transmitted back to the crystal.

•displayed as fuzzy gray echoes below each hyperechoic reverberation echo

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Assumptions

Ring Down

1. Sound travels in a straight line.
2. Sound travels directly to a reflector and back

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Cause

Shadowing

strongly attenuating structures lie in the path of the ultrasound beam

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Description

Shadowing

Distal echoes weaker, appear darker, like a shadow

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Hindrance

Shadowing

Prevents visualization from true anatomy on scan by covering anatomy with an anechoic shadow

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Helpful

Shadowing

Is often useful to determine the nature of masses and structure

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Assumption

Shadowing

Characteristics of the tissue creating the reflection determine the strength of the reflection.

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Cause

Dirty Shadowing

occurs at the tissue-gas interface. When sound hits gas it scatters.

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Appearance

Dirty Shadowing

very cloudy, dirty appearance

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Assumptions

Dirty Shadowing

1. Sound travels in a straight line.
2. Sound travels directly to a reflector and back

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Cause

Enhancement

appears as hyperechoic regions distal to weakly attenuating structures

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Assuptions

Enhancement

Characteristics of the tissue creating the reflection determine the strength of the reflection.

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Benefit

Enhancement

can provide confirmation of fluid component within structure

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Cause

Focal Enhancement

band occurs at the center of the sound beam where the intensity is the strongest.

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Assumption

Focal Enhancement

Characteristics of the tissue creating the reflection determine the strength of the reflection.

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Cause

Rver

sound beam hits a very reflective surface and as they are heading back

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Assumption

Mirror image

2. Sound travels directly to a reflector and back

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Cause

Lobes

beams that travel in a direction other than the direction the main beam is traveling

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Assumption

Lobes

Reflections occur only from structures positioned in the beam’s main axis.

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Cause

Speed Error

when the beam travels through tissue faster than 1540 m/s

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Assumption

Speed error

3. Sound travels 1540 m/s in soft tissue