ACOUSTIC GENERATION OF INTRAARTERIAL CONTRAST BOLUSES

Microbubbles generated by ultrasonic cavitation in vivo might be useab le as flow indicators in some situations instead of injectable contras t agents. Knowledge of those vascular microbubble-generating ultrasoni c fields which produce from negligible up to significant damage will h elp improve guidelines for more effective, safer diagnostic and therap eutic ultrasound, Microbubble boluses have been generated by a 1.8-MHz , focused sound field in the in vivo canine abdominal aorta. Spatial p eak acoustic intensities of 19,000 W cm(-2) generated microbubble bolu ses when exposure was longer than 12 ms, whereas intensities greater t han 4300 W cm(-2) generated a bolus when exposure was for 250 ms. The onset time of these boluses (less than one cardiac cycle) is unachieva ble with intravenous contrast injection. With optimized waveforms and focusing, acoustic bolus generation may prove to be an effective, mini mally invasive method for fast performance of certain selective angiog raphy.