Precisely controlled cavitation during the perfluorocarbon nanodroplets assisted HIFU surgery

The previous study has demonstrated that pulsed HIFU with tens of microseconds pulse duration and 10kHz pulse repetition frequency is effective for cavitation generation. With the assistance of perfluorocarbon (PFC) nano-droplets, cavitation can be further enhanced. But despite higher efficiency, we also need precisely controlled cavitation for sake of therapeutic safety. In this work, we propose a combinatorial ultrasound wave sequence to realize precisely controlled cavitation in PFC nano-droplets assisted HIFU ablation. The applied combinatorial wave sequence was composed of a preconditioned continuous wave sustained for several seconds, then a pause and eventually the pulsed waves. We employed sonoluminescence (SL) to visualize the cavitation active spots. The luminous area and mean light intensity were measured to represent cavitation area and intensity, respectively. High-speed photography was utilized to record the thermal ablation development process. The results showed that cavitation distribution space became more confined and less stretched when sonicated by the combinatorial sequence. The SL area decreased about 60%. Meanwhile, no obvious change in the mean intensity. Higher efficient and better-controlled cavitation and ablation were achieved through applying the combinatorial ultrasound wave sequence.