ECHO 2013 / Artifacts of Imaging and Doppler Know Your Physics
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Attenuation Artifact: Enhancement
Ultrasound Property
Attenuation (penetration) of sound varies with the tissue
Half-power: |
air |
< lung < |
bone |
< muscle < |
soft tissue < blood |
|
Depth(cm) |
0.08 |
0.05 |
0.7-0.2 |
1-0.6 |
5-1 |
15 |
|
|
|
|
|
|
|
• Enhancement
– Sound less attenuated through fluid or absent tissue
– Enhanced echoes may be mistaken for differences in tissue scatter
Propagation Path Artifacts
Propagation path
Reverberations
Nearfield clutter
Multipath
Refraction
Ultrasound MachineMirrorAssumptionsimage :
1. Transmitted waves travel in a straight line from the
Side lobe and grating lobe
transducer
2.All echoesoriginateSpeedalongErrorthe axis of the transducer only
Range Ambiguity
3.Sound waves travel at 1540 m/s in human soft tissue
therefore the distance to a reflector is proportional to the round trip time (13 s/cm)
Propagation Path Artifacts: Reverberations
Secondary reflections that occur along path of a sound pulse, delaying return of signal to transducer and resulting in targets being displayed multiple times at successively greater depths.
Reverberations can occur between
target and transducer
A multiple of the distance to the original structure; amplitude of motion may be exaggerated
two targets
even multiples of distance between targets; motion change similar
Classic TEE Reverberation
Artifact
PA
Transducer is the “reflector”
Reverberation (Mirror) Artifact
TEE: High esophageal view of ascending aorta
Clues to Artifact:
•Motion identical to another real structure
–amplitude and frequency at a multiple of the real structure
•Indistinct edges
•Color flow passes through it
Reverberation Artifact
How many HeartMate II LVAD inflow cannulas are there?
Propagation Path Artifacts:
Reverberations
Reflectors
Ultrasound Property
Perpendicular, strong specular primary reflectors may create sound waves that are secondarily reflected by another
reflector (either from transducer itself or other object)
Reverberations
Multiple echoes created by a ―ping-
pong‖ effect
First or second reflections closest to the transducer are probably real (and act as the reflectors)
This ―ping-pong‖ effect continues until all the energy of the ultrasound is attenuated
Patient with Heartmate II LVAD
Reverberations: Near Field
Clutter
Near Field Clutter or Ring-down Artifact
When ultrasound strikes a strong interface (gas or bone) numerous secondary reverberations may be produced, causing a series of parallel echogenic lines, extening into the tissue.
• Correction:
•Optimize TGC’s
•Move focus
•Multiple views
•B mode and color Doppler
•Contrast agents
Ringdown Artifact
Ring-down Artifact: Reverberations echoes (dense lines) associated with continuous “ringing” of the crystal leading to indiscrete “fuzzy, gray” echoes displayed below each reverberation
Artifact
St. Jude’s AVR: Partial
Thrombosis
Comet-tail Reverberation: Similar in origin to Ringdown artifacts, excessive
“ringing” of echoes from highly reflective objects (mechanical disc) cause reverberations of closely spaced echoes that merge and result in a high amplitude
“tail” .