Investigation of the energy shielding of kidney stones by cavitation bubble clouds during burst wave lithotripsy

TL;DR

This study combines experiments and simulations to analyze how cavitation bubble clouds shield kidney stones from burst wave lithotripsy, revealing up to 80% energy loss and a potential real-time monitoring method.

Contribution

It provides the first quantitative analysis of bubble cloud energy shielding during burst wave lithotripsy using combined experimental and numerical approaches.

Findings

Bubble clouds can block up to 80% of incident wave energy.

A linear correlation exists between acoustic scattering and energy shielding.

Results suggest implications for improving lithotripsy efficacy.

Abstract

We conduct experiments and numerical simulations of the dynamics of bubble clouds nucleated on the surface of an epoxy cylindrical stone model during burst wave lithotripsy (BWL). In the experiment, the bubble clouds are visualized and bubble-scattered acoustics are measured. In the numerical simulation, we combine methods for modeling compressible multicomponent flows to capture complex interactions among cavitation bubbles, the stone, and the burst wave. Quantitative agreement is confirmed between results of the experiment and the simulation. We observe and quantify a significant shielding of incident wave energy by the bubble clouds. The magnitude of shielding reaches up to 80% of the total acoustic energy of the incoming burst wave, suggesting a potential loss of efficacy of stone comminution. We further discovered a strong linear correlation between the magnitude of the energy shielding and the amplitude of the bubble-scattered acoustics, independent of the initial size and the void fraction of the bubble cloud within a range addressed in the simulation. This correlation could provide for real-time monitoring of cavitation activity in BWL.