Cavitation Inception by Dual-Frequency Excitation in High-Intensity Focused Ultrasound Treatment

In our previous study, we proposed a "triggered high-intensity focused ultrasound (HIFU)'' exposure sequence, in which a high-intensity triggering pulse was irradiated just before CW heating waves, to accelerate HIFU treatment. In this study, the second-harmonic was superimposed to the triggering pulse, and the cavitation threshold was investigated by comparing different schemes of second-harmonic superimposition including the case of single-frequency exposure through detecting the subharmonic emission and high-speed camera observation. The experimental results show that cavitation bubbles can be generated most efficiently by using negative-peak-pressure emphasized waves followed by positive-peak-pressure emphasized waves. (C) 2011 The Japan Society of Applied Physics