Speaker: Tim Colonius
Title: Modeling and Simulation of Cavitation and Kidney Stone Comminution in Shockwave Lithotripsy
Affiliation: California Institute of Technology
Date: Friday, January 20, 2006.
Place and Time: Room 101 - Love Building, 3:35-4:30 pm.
Refreshments: Room 204 - Love Building, 3:00 pm.

Abstract. In shockwave lithotripsy (SWL), focused shockwaves are aimed at kidney stones to break them up into fine enough pieces to be passed naturally. Some basic design parameters of lithotripters have been established for many years, but the precise mechanisms that control damage are still debated. Cavitation, in particular, can both enhance and attenuate stone comminution, and must be understood in order to improve lithotripter design. In our work, numerical simulations are used to investigate shock propagation and the consequent growth and collapse of a bubble cloud in the focal region. In the simulations, a continuum two-phase flow model for the ensemble-averaged macroscale is coupled to simplified models for individual spherical bubble dynamics at the microscale. The collective collapse of the bubble cloud provides significant energy for comminution (beyond what a single bubble would produce). Laboratory data is used together with the simulations to establish the importance of cloud interaction effects on treatment parameters such as shock strength and pulse repetition frequency. We will also discuss recent work where we are simulating dynamic fracture of kidney stones and studying a number of fundamental issues related to the non-spherical collapse of cavitation bubbles near the surface of a stone.