Ultrasonic toxicity study

Ultrasound in a delivery format similar to that used clinically in pulse echo diagnostic techniques (1 MHz frequency range, 1000 Hz pulse repetition frequency—peak spatial and temporal intensities and pulse width are larger than those used clinically) has been applied to the male mouse testicles, non-pregnant female mouse ovaries and pregnant mouse uterus at day 8 of gestation. The time average spatial peak intensity for a 20 sec irradiation period at each matrix site for onset of adult mortality in the males and non-pregnant females is essentially 70 W/cm². These data are for a focused beam having a 6 dB beam width of 2 mm. For the pregnant animals, adult mortality begins at 23 W/cm². Significant changes in litter size occur for similar intensity levels. When anomalies which occur in controls are significantly increased for irradiated animals (a striking feature of this study is the almost total lack of appearance of anomalies in irradiated animals which are not present in controls), this increased incidence is not always presented in a unidirectional manner as a function of increasing average intensity. As the average intensity levels are increased in grades to 180 W/cm² there is generally an increased incidence of a given bioeffect. There are, however, some notable exceptions to this generalization. When a 6 dB beam width of 4 mm is used with the pregnant animals the adult mortality begins at 8 W/cm².