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

To develop a noninvasive method for treatment of uterine fibroid tumors using high-intensity focused ultrasound. Optimal high-intensity focused ultrasound treatment would be dependent on quantitative information about ultrasonic tissue characteristics.

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 technique before and after in vitro high-intensity focused ultrasound treatment (3.5 MHz at an intensity of 2,000 W/cm2).

The ranges of the attenuation coefficients, before and after high-intensity focused ultrasound treatment, were 0.9 to 2.2 and 1.8 to 3.9 dB/cm2, respectively, for fibroid tumors and 0.5 to 1.6 and 1.7 to 3.3 dB/cm2, respectively, for myometrium. Although the sound speed appeared to be independent of frequency (1,611 to 1,616 m/s at 1 to 3 MHz) in both types of tissues, a slight increase of approximately 4 to 14 m/s was observed after high-intensity focused ultrasound treatment.

The results of this study represent our first reported values of the attenuation coefficient and sound speed in fibroid tumors and myometrium before and after high-intensity focused ultrasound treatment.