Temperature rise recorded during lesion formation by high-intensity focused ultrasound

Temperature rise was observed as a function of time in liver and dog prostate tissue ex vivo during heating with high-intensity focused ultrasound, The temperature rise was measured using a needle thermocouple placed at the focus, The temperature vs, time behaviour closely followed the predictions of a model based on bulk and surface heating, When the tissue temperature was raised above 50 degrees C, an increase in heating rate was seen, At higher temperatures, a point was reached at which a marked, irreversible change of tissue properties was observed, consistent with protein denaturation, The change was sometimes accompanied by a sudden further rise in temperature followed by an equally sudden fall, On dissection, regions of tissue damage (lesions) were seen, sometimes containing bubbles consistent with acoustic cavitation or vaporisation. (C) 1997 World Federation for Ultrasound in Medicine & Biology.