Cancer treatment by ultrasound: Increasing the depth of necrosis

Tissue coagulation by high-intensity ultrasound is a well-established method of cancer treatment. It suffers, however, from insufficient depth of action in the case of deep-seated tumors where endoscopic or interstitial applicators are used. It is demonstrated here that this depth can be increased by temporarily creating cavitation bubbles in such a way that ultrasound attenuation becomes stronger in the zone where tissue heating is insufficient. In vitro experiments in liver tissue confirm that bubbles are indeed located in this zone and that the effective depth of coagulation necrosis is doubled.