10303 Temperature distribution in the medium with microbubbles in the focused ultrasound field

HIFU (High Intensity Focused Ultrasound) treatment combined with microbubbles as a heat transducer has currently been investigated. It has been indicated that microbubbles have a potential to enhance the heat deposition around the focal region of ultrasound. In order to realize this method, it is needed that the coagulation region in the tissue which contains microbubbles is well-controlled. In this study, the temperature distribution in the medium with microbubbles is analyzed in detail. This time, a thermal liquid crystal (TLC) sheet is used for the measurement of temperature distribution in a polyacrylamide gel. In the case of no bubbles, the shape of the high temperature region was ellipse. In the case of some bubbles, the shape grew more complicated and its area became larger. The microbubbles radiate heat energy around them, and the attenuation effect of ultrasound becomes larger. In the case of too many bubbles, the temperature at the geometric focus didn't become so high. The bubbles shield the most of ultrasound energy. It is very important to choose the optimal conditions of microbubble-enhanced HIFU treatment, considering these phenomena.