Models for cavitation-induced displacement, stress, and strain in tissue.

Abstract

Cavitation activity near tissue interfaces may cause the tissue to deform, inducing stresses and strains of sufficient magnitude to cause damage. Understanding the interaction between bubbles and the surrounding tissue is therefore critical in therapeutic ultrasound. Since interacting bubble clusters are often responsible for bio-effects, both bubble-bubble and bubble-tissue interactions should be considered. In this presentation, simulation results from models describing the dynamics of single bubbles and bubble pairs immersed in a viscous liquid near tissue interfaces will be presented for two geometries. The first geometry is that of a bubble pair positioned between parallel tissue layers, and the second is for a bubble in a viscoelastic cylindrical tube. Tissue displacements caused by the motion of the bubbles may be estimated via models derived using Green’s function and Lagrangian mechanics approaches. The Green’s function approach further permits estimation of the time-varying strain and stress fields in the tissue, including effects of viscoelasticity. Aspherical bubble deformation and the onset of jetting due to bubble-bubble or bubble-tissue interaction is modeled using the Lagrangian mechanics approach. Simulations illustrating the dynamics of the bubbles and tissue for clinically relevant parameters will be presented. [Work supported by NIH Grant Nos. DK070618 and EB011603.]