Attenuation coefficient and sound speed in human myometrium and uterine fibroid tumors

Objective. To develop a noninvasive method for treatment of uterine fibroid tumors using high-intensity focused ultrasound. Optimal high-intensity foc used ultrasound treatment would be dependent on quantitative information ab out ultrasonic tissue characteristics. Methods. Ultrasonic attenuation and the sound speed of fresh human fibroid tumors and myometrium were measured as a function of frequency (1-3 MHz) by using a pulse transmission techniqu e before and after in vitro high-intensity focused ultrasound treatment (3. 5 MHz at an intensity of 2000 W/cm(2)). Results. The ranges of the attenuat ion coefficients, before and after high-intensity focused ultrasound treatm ent, were 0.9 to 2.2 and 1.8 to 3.9 dB/cm(2), respectively for fibroid tumo rs and 0.5 to 1.6 and 1.7 to 3.3 dB/cm(2), respectively, for myometrium. Al though the sound speed appeared to be independent of frequency (1611 to 161 6 m/s at 1 to 3 MHz) in both types of tissues, a slight increase of approxi mately 4 to 14 m/s was observed after high-intensity focused ultrasound tre atment. Conclusions. The results of this study represent our first reported values of the attenuation coefficient and sound speed in fibroid rumors an d myometrium before and after high-intensity focused ultrasound treatment.