What causes reverberation artifact?
Reverberation artifact occurs when an ultrasound pulse gets "trapped" between two strong parallel reflectors. The wave reflects back and forth between the reflectors ("reverberates"). The waves that return to the transducer are interpreted as deeper structures since they arrive to the transducer at a later time.
Reverberation artifact from the skin surface when using a standoff pad. Ghostly reverberations deep to the strongest artifact can also be seen.