A model for the dynamics of gas bubbles in soft tissue

Abstract

Understanding the behavior of cavitation bubbles driven by ultrasonic fields is an important problem in biomedical acoustics. Keller-Miksis equation, which can account for the large amplitude oscillations of bubbles, is rederived in this paper and combined with a viscoelasticmodel to account for the strain-stress relation. The viscoelasticmodel used in this study is the Voigt model. It is shown that only the viscous damping term in the original equation needs to be modified to account for the effect of elasticity. With experiment determined viscoelasticproperties, the effects of elasticity on bubble oscillations are studied. Specifically, the inertial cavitation thresholds are determined using Rmax∕R0, and subharmonic signals from the emission of an oscillating bubble are estimated. The results show that the presence of the elasticity increases the threshold pressure for a bubble to oscillate inertially, and subharmonic signals may only be detectable in certain ranges of radius and pressure amplitude. These results should be easy to verify experimentally, and they may also be useful in cavitation detection and bubble-enhanced imaging.