HIGH-INTENSITY FOCUSED ULTRASOUND ABLATION OF THE KIDNEY IN A LARGE ANIMAL-MODEL

The purpose of this study was to establish the feasibility of noninvas ive treatment of small renal tumors with high-intensity focused ultras ound (HIFU). A 1.69-MHz extracorporeal HIFU transducer of 150-mm focal length was used, In vitro experiments with excised porcine kidneys al lowed determination of suitable exposure parameters to be tested in vi vo. For short exposure times (<2 seconds), the minimum energy required to produce acute thermal damage was 500 +/- 100 Wcm(-2) per second, P orcine kidneys (N = 18) were treated in vivo at a depth of 40 mm from the skin surface, with acute damage detected in 13. Damage was macrosc opically and histologically discrete and confined to the target area w ithin the kidney, Skin induration was observed after treatment in nine cases, and there was one skin burn, Transducer developments to preven t this morbidity and to improve energy deposition within the target ar e discussed.