What is an artifact?
Unintended information on an image that does not represent the object
What is an error in imaging called?
Artifact
What are the 6 assumptions of imaging systems?
- Sound travels in a straight line
- Sound travels directly to a reflector and back
- Sound travels at exactly 1540 m/s
- Reflections arise only from structures positioned in the beams main axis
- The imaging plane is very thin
- The strength of a reflection is related to the characteristic of the tissue creating the reflection
What is the artifact that has multiple, equally spaced echoes?
Reverbation
What is reverberation caused by?
Bouncing of the the sound waves between 2 strong reflectors positioned parallel to the ultrasound beam; Multipath reflection
With reverberation, what echoes are real?
Only the first 2 reflection
What assumption is broken with reverberation?
2 sound travels directly to a reflector and back
(With reverb. large amp echo returns to transducer but gets partially reflected at transducer face over and over)
If there is fill in between the reverb echoes, what does that produce?
Pseudomass
What are the types of reverberation?
Ring down, comet tail, mirror image
What type of artifact occurs due to metallic objects?
Comet tail
What is a dense collection of echoes (closely spaced reverberation merged)
Comet tail
What type of artifact is caused by gas?
Ring down
Why does ring down artifact occur?
From resonance (vibration) of small structures such as gas bubbles
What type of artifact occurs with lipids?
Ring down
What artifact appears as a single, long, hyperechoic echo parallel to beam axis?
Ring down or comet tail
What type of artifact is caused by lipids?
Ring down
What assumption is broken with ring down?
2
When sound bounces off a strong reflector in its path and redirects the pulse laterally towards a second reflector, what artifact occurs?
Mirror image
T/F With mirror image, the reflection is displaced at a closer depth
False; deeper
T/F With mirror image, the artifact and true reflector are equal distances from the mirror
True
What is crosstalk?
Mirror image artifact that appears on a spectral Doppler display
Why does crosstalk occur?
Doppler gain is set too high
What artifact does a high attenuating structure cause?
Shadow
What artifact is caused by the reflectors brightness absence or reduction?
Shadow
