A search for ultrasonic cavitation within the canine cardiovascular system

Abstract Resonant bubble detectors (RBD) were used to search for both pre-existing bubbles and bubbles created by cavitation within the cardiovascular system of 22 dogs. No pre-existing bubbles of 3.8 μm diam or larger were found, nor were any created by exposing the left ventricle to 0.51–1.61 MHz ultrasound of up to 16 W/cm 2 spatial-peak intensity. Bubbles introduced into the arterial system by high speed injection were readily detected and could be held in the heart by 1 MHz ultrasound at 1–2 W/cm 2 or above. A surprising observation was that gas bubbles of resonant size injected into the left ventricle and held by ultrasound did not multiply continuously as happens in saline or water in vitro . This in vivo system was designed to assess the potential for cavitation bioeffects and the essentially negative results obtained may limit the expected or potential risk of this mechanism in regard to medical applications of ultrasound.