Ultrasound Artifact Flashcards
Artifact
Echos that don’t represent true tissue or pathology.
Useless Artifact
Hampers evaluation
Useful Artifact
Provide some informationabout the nature of the structures. Provide evidence of technique that can be improved(gain, TGC settings, improper skin coupling). Can show gas, food or feces.
Acoustic Shadowing
Reflective and Refractive
Reflective Shadowing
Most sound waves are reflected back, leaving a bright interface and strong distal shadow.
Clean or Complete Shadows
Associated with calculi, bone, solid feces, barium of pure gas.
Dirty or Incomplete Shadow
Mixed echogenicity with fuzzy edges. Usually associated with gas and air-filled structures, reverberation plays a large role. Also seen with semisolid material(cloth, soft stool, food).
Refractive “Edge Shadowing”
Sound is bent(refracted) at a curved interface and doesn’t reflect back to transducer creating an echo free zone below the point where the beam bends.
Far Field Enhancement
Acoustic enhancement through transmission. Sound travels well through water and similar tissues with no interfaces with minimal attenuation. The result is interfaces deep to a fluid filled structure have stronger returning echos.
Use to differentiate fluid from hypoechoic.
Side Lobe Artifact
Echos reflected back from side lobes as if they were in main beam, so echos from side lobes are placed in main beam image at appropriate depths.
Changing focus location should change artifact.
Mirror Image
Large, curved highly reflective surfaces form a reverberation or refractive artifact.
Specular Reflectors
Diaphragm, Gall bladder, pericardium(because of strong reflection of the air-filled lung)
Reverberation
“Comet Tails” or “Ring Down”
Hyperechoic, equally spaced lines, “fuzz”.
Small, highly reflective interfaces found close together cause sound to bounce back and forth between structure and transducer or resonate within the structure.
Resolve by finding a different window.
Speed Propagation Error
Time vs Distance relationship is based on assumption that sound speed is constant at 1540 M/sec in most biologic tissues(average soft tissue velocity) and this is used to calibrate distance. When encountering tissues with other velocity, life fat at 1450 M/sec, this difference is not accounted for and distance measurments will be inaccurate.
Twinkling Artifact
Color phenomenon during color doppler imitating turbulent blood flow where there isn’t movement.
Average Soft Tissue Velocity
1540 M/sec
1450 M/sec
Fat, average fat tissue velocity
