[Study on therapeutic dosimetry and biologic effect of high intensity focused ultrasound]

This study was aimed at exploring the high intensity focused ultrasound(HIFU) therapeutic dosimetry and its biologic effect. In-vitro, bovine liver was immersed into 0.9% NS and degassed for application. The JC Model-focused ultrasound tumor therapeutic system was used in the experiment. The HIFU parameters were: frequency 1.6 MHz, depth 20 mm, acoustic power from 16.44 W to 196.32 W. Under each power, at radiating times from is to 20 s, bioptic specimens were obtained from all samples. The results showed when the acoustic power was equal to or higher than 179.96 W, only is of radiating is adequate to induce coagulative necrosis, and when the acoustic power was lower than 65.44 W, the radiating time to produce coagulative necrosis was about 7 s. In the range of 65.44-179.96 W, at each time when the acoustic power was set up with an increment of 16.36 W, the time to produce coagulative necrosis was 1-2 s shorter. The form of biological focal region (BFR) varied with the acoustic power and HIFU irradiation time. The size of BFR increased with the increase of HIFU irradiation dosage (acoustic power x exposure time). There is positive correlation between the size of BFR and the dosage of HIFU irradiation (y = 0.0164x(1.05591), R5 = 0.9238, P < 0.05).