Laser ablation for prostate tumors: analysis of different bioheat transfer models

Thermal therapies, such as laser ablation, are garnering interest for treating several diseases, in a non-invasive way, preventing surgical treatments and, for example, allowing the preservation of prostate functions in the case of prostate cancer. Nevertheless, approved therapies for cancer treatments are still missing, limiting the reliability of such methodologies, since an insufficient exposure time and thermal power settings could lead to incomplete tumor ablation, its redevelopment and metastasis occurrence. Consequently, it is fundamental to develop accurate bioheat transfer models providing guidelines to surgeons, helping to improve treatment effectiveness. However, as several models have been developed, the study aims to compare four bioheat transfer models, namely the simplified Pennes' approach, two porous media-based methods, i.e. the Local Thermal Equilibrium and the Local Thermal Non-Equilibrium equations, and the non-Fourier approach, namely Dual Phase Lag equation. The effects of laser power, tissue porosity and blood vessels diameter are investigated. The finite elements (FEM) commercial software Comsol Multiphysics is employed to investigate a 2D axisymmetric domain, consisting of two concentric spheres (the tumor and the healthy tissue). The laser source is modeled with the Beer-Lambert's law, assuming a laser source with a gaussian distribution. Results in terms of temperature field and necrotic region are presented, developing linear correlations by fitting FEM results. Finally, the difference among the necrotic areas predicted with the different approaches is reported, providing high discrepancies especially for highly vascularized tissue, with a lower damaged surface predicted in case of porous media approaches.