High-intensity focused ultrasound (HIFU) treatment is a noninvasive treatment, in which focused ultrasound is generated outside the body and coagulates a diseased tissue. The advantage of this method is minimal physical and mental stress to the patient, and the disadvantage is the long treatment time caused by the smallness of the therapeutic volume by a single exposure. To improve the efficiency and shorten the treatment time, we are focusing attention on utilizing cavitation bubbles. The generated microbubbles can convert the acoustic energy into heat with a high efficiency. In this study, using the class D amplifiers, which we have developed, to drive the array transducer, we demonstrate a new method to coagulate a large volume by a single HIFU exposure through generating cavitation bubbles distributing in a large volume and vibrating all of them. As a result, the coagulated volume by the proposed method was 1.71 times as large as that of the conventional method.
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