Ultrasonically induced cavitation in mammals

Abstract

The role of cavitation in the production of biological effects in mammals is reviewed with emphasis on recent studies in the mouse neonate. The levels for hind limb paralysis from 1 MHz, continuous wave unfocused ultrasound in the neonatal mouse, within 24 h of birth, have been investigated at 1 and 16 bars ambient pressure and temperature between 10° and 37°C. Above certain intensity levels the exposure duration for paralysis of 50% of specimens exposed increases with increased ambient pressure. Since an increased ambient pressure tends to suppress cavitation, such changes suggest cavitational involvement. Results show that cavitation may be involved in the resultant paralysis above approximately 150 W/cm2 at 10°C, and above approximately 60 W/cm2 at 37°C. This temperature dependence is consistent with a cavitation mechanism. [Work supported by National Institutes of Health.]