Numerical analysis of radiofrequency ablation in a tumour tissue bounded by healthy tissue

Medical interest in thermoablation of tumours is growing more and more throughout the years, because it is a minimally invasive treatment which yields few complications, a short hospital stay and low costs. The interest of the thermoablation is to destroy completely the tumour without further recurrence and save the surrounding healthy tissue from the high temperatures. Computer modelling of the specific treatment has a key role in predicting effectiveness of the technique since it allows to compute the coagulation zone and temperature profiles in tumour tissues. In this study we focus on a computer model for a 12-min radiofrequency ablation (RFA) of in vivo liver tissue using a cooled electrode. The model is based on the porous media approach and employs a Local Thermal Non-Equilibrium (LTNE) equations modified in order to take into account the vaporization of water in the two phases (tissue and blood). The LTNE equations are applied separately in two different cases: healthy liver tissue and a tumoral tissue surrounded by healthy tissue. Governing equations with the appropriate boundary conditions are solved with the finite-element code COMSOL Multiphysics®. The results are presented in terms of coagulation zones transverse diameters and temperature fields obtained at the end of the application. Furthermore, temperature evolution in three different points during the 12-min ablation is evaluated. The outcomes show relevant differences when the tumour is included in the model. Thus, the different electrical conductivity and thermal properties between the two types of tissues play a fundamental role in the outcomes.