Reflector geometry and pressure at the focus of a shock wave lithotripter

Abstract

It has been experimentally shown [Zhong, J. Acoust. Soc. Am. 113, 586–597 (2003)] that refinement of the geometry of the HM-3 lithotripter reflector suppressed the expansion of cavitation bubbles without compromising stone comminution. This effect has been attributed to a change in the rarefaction tail of the pressure wave near the second focus of the original reflector (F2). Following this idea, a numerical model of the reflection and steepening of a pressure wave from an axisymmetric lithotripter has been developed. The model is based on the Euler equations coupled with the Tait equation of state. Preliminary results of the pressure fields produced by numerous reflector shapes are presented. The results show the changes in the rarefaction tail of the pressure wave near F2 for different geometries, thus hinting at the possibility of optimization of the reflector shape for an ideal waveform. [Work supported by NSF.]