The effects of ultrasonically induced hyperthermia on experimental tumors in the rabbit eye

Greene's melanomas, implanted in the anterior chamber of 31 eyes of 19 Dutch rabbits, were treated with hyperthermia induced by high intensity focused ultrasound (HIFU). The percentage necrosis 24 hr after treatment (N) as a function of steady-state intratumor temperature (T) could be described with N(T) = -181.5 + 4.7T (P less than 0.05). The most frequent side effect was a local hemorrhagic keratitis. The acoustic absorption coefficient and thermal conductivity of the tumor tissue were 0.08 cm-1 X MHz-1 at 36 degrees C and 0.011 W, cm-1 X degrees C-1, respectively. With these parameters a simple thermal model was established that enabled us to predict the ultrasonic intensity needed to reach a desired intratumor temperature.