Publications (2)3.1 Total impact
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Article: High-intensity focused ultrasound heating of large tissue region enhanced by cavitation bubbles at multiple focal spots.
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ABSTRACT: High-intensity focused ultrasound (HIFU) causes selective tissue necrosis through heating and is used for a noninvasive treatment of cancer therapy. However, it has a problem of a long treatment time for a large tumor. To improve the throughput of the treatment, the development of a highly efficient method is needed. It is known that cavitation bubbles enhance the heating effect of ultrasound during ultrasonic irradiation because the increase in the energy dissipation is caused by the volumetric oscillation of cavitation bubbles. In this study, cavitation bubbles were generated at multiple spots by changing focal position of high-intensity ultrasound. Immediately after generating the bubbles, the bubbles were exposed to a wide-focused ultrasound which covers all the cavitation sites for the cavitation-enhanced heating in a large region. The behavior of the cavitation bubbles at multiple spots in a tissue-mimicking gel was observed by high-speed photography, and the coagulation performance of the developed sequence was confirmed with an experiment using excised tissue. The results showed high efficacy of the proposed method for to coagulate a large tissue region.The Journal of the Acoustical Society of America 04/2012; 131(4):3364. · 1.55 Impact Factor -
Article: Optically transparent gel for experimentally mimicking cavitation enhanced ultrasonic heating of tissue.
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ABSTRACT: High intensity focused ultrasound (HIFU) is a noninvasive method for cancer treatment. However, there is a problem of a long treatment time for treating a large volume. It is known that cavitation bubbles, generated by extremely high intensity ultrasound pulses, enhance the heating effect of HIFU. In order to investigate a cavitation-enhanced highly-efficient method of HIFU, an optically transparent gel with both ultrasonic absorption and cavitation threshold similar to biological tissue is being developed. Such a polyacrylamide (PAA) gel was successfully produced by controlling the concentrations of both acrylamide and albumin. The effect of cavitation bubbles enhancing the ultrasonic heating was measured using the gel by exposing it to HIFU. The effect was considered in the bio-heat transfer equation (BHTE) by increasing the ultrasonic absorption coefficient in the region of the cavitation, whose volume was determined by high-speed-camera observation. The absorption coefficient was calculated by fitting between the temperature rise curves at the focal point in the experiment and numerical simulation. The simulation using the obtained absorption coefficients of the gel with and without cavitation showed overall agreement with the experiment using the gel. The developed gel and method will be useful for further development of this HIFU method.The Journal of the Acoustical Society of America 04/2012; 131(4):3365. · 1.55 Impact Factor
