Recent bioeffects studies with ultrasound on the reproductive system and solid tumors

Abstract

The reproductive system of the mouse and the pregnant mouse uterus studied under both pulsed and continuous wave regimes display a spectrum of responses. There is generally an increased incidence of response as the time average intensity is increased. Some notable exceptions exist to this general trend. These studies have used focused beams of 2 and 4-mm diameter at the 6-dB points. A given organ is covered by multiple-site exposure in a serial time sequence. In this way more nearly organ-specific irradiations can be conducted and paralysis due to spinal cord irradiation or anal musculature destruction is avoided for exposure at average intensities necessary to elicit the bioeffects observed in the study. A variety of ultrasound regimes have been studied and the time average intensity and exposure times reduced to the levels at which no statistically significant difference exists between exposed and control animals for the bioeffects being scored. Solid tumors grown in the hamster flank by innoculation with cells derived from a Simian medulloblastoma have been irradiated with 720-W/cm2 focused ultrasound. At 7-s continuous wave irradiation, it is possible to produce tumor extinction, regarded as a cure rate of 33%. The exposure regime has not been optimized.