2 Ch 21: Artifacts Flashcards
Artifacts result from:
- violations of __
- __ malfunction
- __ of ultrasound
- operator __
assumptions
equipment
physics
error
Assumption #1: Sound travels in…
in a straight line.
Assumption #2: Sound travels directly…
to a reflector and back.
Assumption #3: Sound travels in soft tissue…
at exactly 1540 m/s.
Assumption #4: Reflections arise only from…
structures positioned in the beam’s main axis.
Assumption #5: The imaging plane is…
very thin.
Assumption #6: The strength of a reflection is related to…
the characteristics of the tissue creating the reflection.
These appear on the display as multiple equally spaced echoes caused by the bouncing of the sound wave between two strong reflectors positioned parallel to the u/s beam.
reverberation
Reverb violates which assumption?
2 (sound travels directly to the reflector and back)
This artifact appears in multiples, equally spaced, and are located parallel to the sound beam’s main axis, at ever-increasing depths.
reverberation
This appears as a solid hyperechoic line directed downward.
comet tail aka ring down
This artifact is created when closely spaced reverberations merge.
comet tail
Comet tail violates which assumption?
2 (sound travels directly to the reflector and back)
Two characteristics of comet tail?
- a single long hyperechoic echo
2. located parallel to the beams main axis
This appears as a hypoechoic or anechoic region extending downward from a highly attenuating structure.
shadow
Shadows are the same color as the…
image background.
Shadows appear when the __ in the tissue above the shadow than in the surrounding tissue.
attenuation is higher
Shadowing violates which assumption?
6 (reflection strength is related to the tissue creating the reflections)
This artifact is located beneath the structure with abnormally high attenuation and prevents visualization of true anatomy on the scan.
shadowing
T/F? Shadowing is unrelated to the speed of sound in a medium.
true
This is a special form of shadowing that appears as a hypoechoic region extending down from the edge of a curved reflector.
edge shadow aka shadowing by refraction
Edge shadowing violates which assumption?
6 (reflection strength is related to the tissue creating the reflections)
This appears as a hyperechoic region beneath tissues with abnormally low attenuation.
enhancement
Enhancement violates which assumption?
6 (reflection strength is related to the tissue creating the reflections)
This artifact is the opposite of shadowing.
enhancement
T/F? Enhancement artifact is entirely unrelated to the speed at which sound travels in a medium.
true
This is a special form of enhancement in which a side-to-side region of an image appears brighter than tissues at other depths.
focal enhancement aka focal banding
Focal enhancement violates which assumption?
6 (reflection strength is related to the tissue creating the reflections)
This is created when sound reflects off a strong reflector and is redirected toward a second structure.
mirror image