Experimentally validated multiphysics computational model of focusing and shock wave formation in an electromagnetic lithotripter

A multiphysics computational model of the focusing of an acoustic pulse and subsequent shock wave formation that occurs during extracorporeal shock wave lithotripsy is presented. In the electromagnetic lithotripter modeled in this work the focusing is achieved via a polystyrene acoustic lens. The transition of the acoustic pulse through the solid lens is modeled by the linear elasticity equations and the subsequent shock wave formation in water is modeled by the Euler equations with a Tait equation of state. Both sets of equations are solved simultaneously in subsets of a single computational domain within the BEARCLAW framework which uses a finite-volume Riemann solver approach. This model is first validated against experimental measurements with a standard (or original) lens design. The model is then used to successfully predict the effects of a lens modification in the form of an annular ring cut. A second model which includes a kidney stone simulant in the domain is also presented. Within the stone the linear elasticity equations incorporate a simple damage model

Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter

Electromagnetic (EM) shock wave lithotripters are widely used for noninvasive treatment of kidney stone patients. Here, we report the design of a new acoustic lens to rectify three fundamental drawbacks in contemporary EM lithotripters, based on in situ pulse superposition, leading to significantly improved stone comminution both in vitro and in vivo with minimal tissue injury. The new lens design improves the pressure distribution around the lithotripter focus with better alignment of the peak pressure and cavitation activities with the kidney stones under clinically relevant treatment conditions. The general principle of the new lens design is applicable to different lenses or reflectors and with further optimizations may enhance the performance and safety of contemporary EM lithotripters

Experimentally validated multiphysics computational model of focusing and shock wave formation in an electromagnetic lithotripter

A multiphysics computational model of the focusing of an acoustic pulse and subsequent shock wave formation that occurs during extracorporeal shock wave lithotripsy is presented. In the electromagnetic lithotripter modeled in this work the focusing is achieved via a polystyrene acoustic lens. The transition of the acoustic pulse through the solid lens is modeled by the linear elasticity equations and the subsequent shock wave formation in water is modeled by the Euler equations with a Tait equation of state. Both sets of equations are solved simultaneously in subsets of a single computational domain within the BEARCLAW framework which uses a finite-volume Riemann solver approach. This model is first validated against experimental measurements with a standard (or original) lens design. The model is then used to successfully predict the effects of a lens modification in the form of an annular ring cut. A second model which includes a kidney stone simulant in the domain is also presented. Within the stone the linear elasticity equations incorporate a simple damage model