A multiphysics model for radiofrequency activation of soft hydrated tissues

Abstract

A multi-physics model has been developed to investigate the effects of cellular level mechanisms on the electro-thermo-mechanical response of hydrated soft tissues with radiofrequency (RF) activation. A micromechanical model generates an equation of state (EOS) that provides the additional pressure arising from evaporation of intra- and extracellular water as well as temperature to the continuum level thermo-mechanical model. A level set method is used to capture the interfacial evolution of tissue damage with the level set evolution equation derived from the second law of thermodynamics, which is consistent with Griffith’s fracture evolution criterion. The discretized equations are solved simultaneously using a Krylov subspace based iterative solver (GMRES) with block preconditioning that effectively deflates the spectrum of the system matrix, resulting in exponential convergence of the Arnoldi iterations. Example problems, including experimental validation, illustrate the computational accuracy and efficiency of the technique.

Fast computation of soft tissue thermal response under deformation based on fast explicit dynamics finite element algorithm for surgical simulation

“…The blood flow in the capillaries is assumed isotropic and hence the directional-dependent blood flow heat transfer is not modelled [19,54]. The physical processes such as water evaporation and transport of vapor are not captured in the classical PBHT [25,37,55]; however, the phase change occurs when tissue temperature elevates beyond the vaporisation threshold 𝑇 𝑡ℎ𝑟𝑒𝑠 (𝑇 𝑡ℎ𝑟𝑒𝑠 = 100℃ [36]), but the maximum temperature reached in the present work is less than 𝑇 = 65℃ (see Fig. 4(a)).…”