ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

4aPAb6. Cavitation from short pulses high-frequency ultrasound: A study of cavitation production rates and their dependence on acoustical parameters.

Adam Calabrese

Dept. of Phys., Univ. of Mississippi, Oxford, MS 38677

Ronald A. Roy

Univ. of Washington, Seattle, WA 98105

Previously, cavitation due to pulsed megahertz-frequency ultrasound was detected using a technique that only looked for the onset of detectable cavitation [Calabrese et al., Advances in Nonlinear Acoustics, edited by H. Hob(ae ligature)k, pp. 394--399 (1993)]. This method provides little information about cavitation production rates, which may be better correlated to a mechanical bioeffect than the threshold alone. A modified approach using a passive cavitation detector [Roy et al., J. Acoust. Soc. Am. 87, 2451--2458 (1990)] is used to determine the rate of cavitation as a function of acoustic pressure amplitude. Measurements are repeated for a variety of pulse lengths (from 3 to 100 (mu)s) and duty cycles (from 0.1% to 20%) and at frequencies of 1, 2.25, and 5 MHz. Initial results suggest that the threshold pressure for cavitation is weakly dependent on pulse length and decreases with increasing duty cycle. [Work supported by NIH through Grant No. RO1 CA39374.]