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

4aPAb5. Cavitation in water generated by pulse Doppler ultrasound.

Ronald A. Roy

Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98105

J. Brian Fowlkes

Univ. of Michigan Medical Ctr., Ann Arbor, MI 48109

A recently published study reports the direct observation of transient microcavitation in water produced by clinical diagnostic ultrasound [Holland et al., IEEE UFFC 39, 95--101 (1992)]. Results are presented from a similar study in which an aqueous suspension of 0.2-(mu)m-diam polystyrene spheres was insonated by an ATL UM9 scanner operating in the pulse Doppler mode at 3.5 and 5.0 MHz. The suspension was degassed to approximately 90% of saturation. Using a computer automated active cavitation detector [Roy et al., J. Acoust. Soc. Am. 87, 2451--2458 (1990)], cavitation production rates were obtained for a variety of pulse parameters such as intensity, peak negative pressure, pulse length, and pulse repetition frequency. Results suggest a cavitation threshold which is fairly well predicted by the mechanical index calculated from the various pulse waveforms obtained in situ. [Work supported by NIH through Grant No. RO1 CA39374.]