Effects of cavitation in the high intensity therapeutic ultrasound

Tissue destruction with high intensity ultrasound can be explained by the action of two effects: the first is a hyperthermic effect; the second involves physical damage to the cell from cavitation. In the study described, effects of cavitation were investigated as a function of intensity using either shock waves with large negative pulse or a 1-MHz focused field. In the first set of experiments the cavitation was strong enough to achieve focused and deep tissue destruction in the rabbit´s liver. In the second set of experiments, it was shown that when cavitation was moderate no significant effect on tumor growth was achieved. It was thought that in these last experiments, the bubbles that appeared in the field strongly reduced the desired thermal effects of the radiation. It appears, then, that there is a set of optimal parameters that allows the best in vivo tumor treatment