Time-Dependent Acoustic Waves Generated by Multiple Resonant Bubbles: Application to Acoustic Cavitation

TL;DR

This paper analyzes the time-dependent acoustic waves generated by multiple resonant bubbles, with applications to acoustic cavitation therapy, deriving models that predict wave behavior and enable pressure control in targeted regions.

Contribution

It derives a dominant acoustic field model for bubble clusters considering high contrast properties and bubble distribution, highlighting effects like echo enhancement and dispersive behavior.

Findings

Resonant bubble clusters significantly amplify acoustic echoes.

Distributed bubbles lead to a dispersive effective acoustic model.

Model tuning allows pressure control for therapeutic applications.

Abstract

We analyse the ultrasound waves reflected by multiple bubbles in the linearized time-dependent acoustic model. The generated time-dependent wave field is estimated close to the bubbles. The motivation of this study comes from the therapy modality using acoustic cavitation generated by injected bubbles into the region of interest. The goal is to create enough, but not too much, pressure in the region of interest to eradicate anomalies in that region. Here, we derive the dominant part of the generated acoustic field by a cluster of bubbles taking into account the (high) contrasts of their mass density and bulk as well as their general distribution in the given region. As consequences of these approximations, we highlight the following features: 1. If we use dimers (two close bubbles), or generally polymers, then we obtain a remarkable enhancement of the whole echo in the whole time. 2. If we distribute the bubbles every where in the region of interest,then we can derive the effective acoustic model which turns out to be a dispersive one. We show that, for a given desired pressure, we can tune the effective model to generate it.