Effect of acoustic cavitation on platelets in the presence of an echo-contrast agent

A suspension of human platelets in autologous plasma or buffer solution with and without a microbubble echo-contrast agent was exposed in vitro to 730 W/cm(2) (I-SPPA) ultrasound pulses of duration 40-160 mu s at 1 MHz and 20-Hz pulse repetition frequency. Inertial cavitation occurring within the samples was monitored during the exposures and a measure of average cavitational activity was calculated for each 5-min exposure, This quantity, with the other acoustic parameters, accounted for up to 75% of the variation in the destruction of platelets as measured by Coulter counter and 83.5% of the release of bound radiolabel using a multiple-interaction statistical model, When the echo-contrast agent was absent, negligible cavitation occurred and the amount of platelet destruction was statistically indistinguishable from sham (no-ultrasound) exposures, Therefore, microbubble echo-contrast agents may interact with ultrasound to cause platelet lysis through the mechanism of inertial cavitation. (C) 1998 World Federation for Ultrasound in Medicine & Biology.