Acoustic artifacts

Clean shadowing

Loss of information posterior to a highly reflective structure, US bean completely reflected by the structure with no reflections displayed posterior to it, “anechoic” shadowing

Dirty shadowing

Loss of information posterior to highly reflective structure such as air and fatty structures, causes increased scatter, “echogenic” shadowing

Seen with bowel gas

Ring down artifact is associated with the interaction of sound and ______

Air

Grating lobes

Weak axis lobes associated with an array of piezoelectric elements

Causes appearance of misplaced reflections lateral to the actual structure on the image

Side lobes

Weak off axis lobes associated with a single element probe

Noise/Speckle

Result of scattering due to the rough surface characteristics, partial constructive and destructive interference occurs resulting in a “speckle” appearance of tissue

Nyquist limit

Maximum frequency that can be displayed as ½ PRF

Lower PRF, the lower the limit for properly displayed velocity

Clutter

Also called flash artifact

Caused by low color scale settings

Increase color scale and reduce color gain to decrease effect

What artifact occurs posterior to weakly attenuating structures

Posterior enhancement

__________ causes anechoic shadowing, while _________ causes echogenic

Bone; bowel gas

Reverberation is typically seen in the ______ field of view

Anterior

What artifact causes a linear stripe of repeated reflections

Ring down

Mirror image artifact causes the display of false echoes ____________, while lobe artifact causes the display of false echoes ____________

Deeper than actual structure; lateral to the actual structure

How is aliasing artifact corrected?

Switch to CW Doppler

What causes clutter artifact?

Low velocity scale settings