Abstract: Objective To investigate the pathological change in Echinococcus granulosus hydatid cysts treated with high intensity focus ultrasound （HIFU）. Methods Thirty cysts with thinner wall and proper elasticity, taken from livers of infected sheep， were randomly divided into three groups. By cyclical multilayer radiation around the cyst wall，two experiment groups were treated with HIFU under 150 W and 250 W sound power respectively. The control group was treated by ordinary ultrasound for 2 min. Results The inner cyst wall of hydatid treated with HIFU became curved，thicker， stiffer， white and less transparent. The germinal layer was detached mostly from the laminated layers of hydatid in the experiment groups. Images from the transmission electron microscopy showed that in the experiment groups fabric texture of hydatid changed significantly and germinal cells were broken. Conclusion HIFU in a model of cyclical multilayer radiation causes pathological damage of the E. granulosus hydatid.

Key words: High intensity focused ultrasound, Echinococcus granulosus, Hydatid, Pathology