Ultrasonic properties of biliary calculi.

Abstract

The authors show that the intrinsic ultrasonic attenuation of a gallstone is an important factor in determining the degree of shadowing. B scans in vivo and in vitro demonstrated that stones with higher attenuation also show the most shadowing. In addition, attenuation can be correlated with physical structure: more highly attenuating stones tend to have the largest percentage of crystalline material, a larger average crystal size, and a more rigid structure. The authors recommend that higher-frequency transducers be used where possible if nonshadowing structures are seen in the gallbladder.

Advances in hepatobiliary ultrasonography

“…Gallstones invariably greater than 6 mm and those between 3 and 6 mm almost always display typical intense echoes and posterior acoustic shadowing. Highly attenuating stones tend to have a large percentage of crystalline material, a large crystal size, and more rigid structure (50). Occasionally, a stone greater than 3 mm fails to cast a shadow, and according to Gonzalez and MacIntyre (51)) shadowing depends primarily on orientation of the stone in relation to the sound beam.…”