Cavitation in flowing media by lithotripter shock waves in vitro and in vivo

Abstract

Cavitation produced by lithotripter shock waves was characterized in vitro in water and blood, and in vivo in aortic blood by means of a resonant bubble detector. The 1.6‐MHz detector can detect and count 4 ± 1‐μm‐diam bubbles flowing through it by receiving their second harmonic emissions at 3.2 MHz. Spark‐gap lithotripters were used to expose the flowing liquid upstream of the detector at the shock wave focus. This system was readily able to detect bubbles resulting from shock wave‐induced cavitation in both water and blood flowing through plastic tubes in vitro, and even in blood pumped by the heart through a plastic arteriovenous shunt. Multiple (up to several hundred) bubble counts were obtained for each shock wave. However, for 200–400 shock wave exposures of each of two dogs, this system was unable to detect evidence of shock wave‐induced cavitational activity occurring within the intact vascular system in vivo. [Work supported by Dornier Medizintechnik and by NIH Grant CA 42947.]