ACCELERATION OF FOCUSED ULTRASOUND TREATMENT BY HIGH-INTENSITY TRIGGER PULSES

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The generation of cavitated microbubbles which can potentially enhance ultrasonic heating of biological tissue was studied using a high-speed camera. An optically transparent gel with tissue-mimicking ultrasonic properties was developed and used. The generation was confirmed at an ultrasonic intensity more than the order of 10 kW/cm2. It was localized in the focal region at a pulse duration less than the order of 100 μs. The throughput of ultrasonic thermal coagulation of excised tissue was markedly improved by the generated microbubbles. Furthermore, it was discovered that the ultrasonic intensity needed for generating such cavitated microbubbles can be significantly reduced by superimposing the second harmonic to the fundamental.