Modeling of the thermomechanical response of ultrasonically activated soft tissue

Abstract

A multi-physics computational model has been developed to investigate the thermomechanical response of the ultrasonically activated soft tissue. In pursuit of better understanding of the extent of deformation of soft tissues subjected to harmonic excitations, the cellular level cavitational effect has been incorporated in the tissue level continuum model to accurately determine the thermodynamic states such as temperature and pressure. The cavitation model based equation of state (EOS) captures the additional pressure as a result of evaporation of intracellular and cellular water by absorbing heat due to frictional heating in the tissue, and temperature in the continuum level thermomechanical model. The extent of deformation of the soft tissue is studied for the simulated range of frequencies of harmonic oscillations and applied loads. The model is shown to capture characteristics of ultrasonically activated soft tissue deformation and temperature fields. At the cellular level, evaporation of water below 100°C is indicative of protein denaturation and coagulation much below the boiling temperature under ambient conditions. Further, it is revealed that with the increasing operating frequency and loading, the evaporation of water starts earlier, which may lead to accelerated protein denaturation and coagulation.