Dependence on pulse parameters for free radical production by cavitation from short pulsed ultrasound

Recent data will be presented that indicate the presence of free radicals generated with peak acoustic pressure amplitudes and pulse shapes characteristic of some medical diagnostic devices. The free radicals were detected via a chemiluminescence reaction in an aqueous solution containing luminol using a single photon counting technique. The acoustic pressure threshold for light emission was examined as a function of pulse width, duty cycle, and pulse repetition frequency (PRF); possible explanations for these dependences based upon a simple concept of cavitation inception will bc presented. [Work supported by the National Institutes of Health.]