Cavitation Bubble Cluster Dynamics Induced by Lithotripter Shock Wave at Stone Surface
Y.A.Pishchalnikov, O.A.Sapozhnikov (Department of Acoustics, Faculty of Physics, Moscow State University, Moscow, Russia); J.C.Williams Jr., A.P.Evan, J.A.McAteer (Department of Anatomy and Cell Biology, Indiana University, School of Medicine, Indianapolis, IN, USA); R.O.Cleveland (Department of Aerospace and Mechanical Engineering, Boston University, Boston, MA, USA); T.Colonius (Department of Mechanical Engineering, California Institute of Technology, Pasadena, CA, USA); M.R.Bailey, L.A.Crum (Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, WA, USA)
The behavior of cavitation bubbles at the surface of artificial and natural kidney stones during shock wave lithotripsy was investigated in vitro by means of high-speed photography. It was observed that after the passage of the lithotripter shock pulse the stone was covered by numerous individual bubbles. During their subsequent inertial growth and collapse, these bubbles did not remain independent but combined with one another to form larger bubbles and bubble clusters. Thus, the majority of the bubbles were swept away from their original position leaving sections of the stone surface bubble-free. The biggest cluster consistently developed at the front of the stone. This bubble cluster grew to envelope the entire proximal portion of the stone surface and collapsed to a small spot. Multiple shots resulted in the formation of a crater in the proximal surface of the stone. The bubble clusters that grew at the sides of stones tended to align along cracks and to collapse into these fractures. High-speed camera images suggested that cavitation-mediated damage to stones was due not to the action of solitary, individual bubbles, but to the forceful collapse of dynamic clusters of bubbles. [Supported by NIH DK43881].
Section : 5