Effects of high-energy focused ultrasound on kidney tissue in the rat and the dog.

In vivo tissue destruction was performed on 124 rat and 16 canine kidneys by focusing high-intensity ultrasound with a 1- and 2.25-MHz transducer. A precise tissue lesion was obtained in both models which varied in size according to the number of firings and the acoustic intensity. In the rat experiments, which were used to define the constants necessary to produce a localized tissue lesion at the focus of the transducer, the lesions obtained were either coagulating necrosis or a 'punched out' cavity which represented the threshold of tissue ablation. In the canine experiments, a kidney lesion was achieved in 10 animals (63%) extracorporally. These lesions were also histologically determined to be coagulation necrosis. These lesions are created by highly focused ultrasound and are caused most likely by a combination of cavitation and thermal effects, depending on the duration and frequency of the ultrasound bursts. Exact mechanism of this effect is explored as well as potential clinical applications in treating kidney, liver, and prostate tumors in humans.