Abstract
It has been established that inertial cavitation is responsible for elevated heating during high-intensity focused ultrasound (HIFU) application for certain intensity regimes. The contribution of bubble-induced heating can be an important factor to consider, as it can be several times that expected from absorption of the primary ultrasound energy. Working in agar-graphite tissue phantoms with a 1.1-MHz HIFU transducer, an embedded type-E thermocouple, and a 15-MHz passive cavitation detector (PCD), the temperature and cavitation signal near the focus were measured for 5-s continuous wave HIFU insonations. The measured temperature was corrected for heating predicted from the primary ultrasound absorption and the transient thermocouple viscous heating artifact to isolate the temperature rise from the bubble activity. We have found that the temperature rise induced from the bubble activity correlates well with the instantaneous cavitation noise power as indicated by the mean square voltage output of the PCD. The results suggest that careful processing of the cavitation signals could serve as a proxy for measuring the heating contribution from inertial cavitation. [Work supported by the Dept. of the Army (Award No. DAMD17-02-2-0014) and the Center for Subsurface Sensing and Imaging Systems (NSF ERC Award No. EEC-9986821).]
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