Temperature and tissue damage distributions during selective laser hyperthermia of breast cancer models: Effects of different boundary conditions.

This paper deals with the simulation of the selective laser hyperthermia treatment of breast cancer. The physical model refers to a 2-D axi-symmetric (r-z) bio-heat transfer process due to a laser radiation that propagates inside breast tissues containing a spherical tumor loaded with gold nanoparticles. The corresponding bio-heat transfer process is governed by the equation of Pennes, while the laser light propagation is modeled with the diffusion approximation. The solution of this opto-thermal problem was obtained using the Finite Element Method (FEM), whereas the thermal damage that occurs in tissues was calculated from the Arrhenius equation. First simulation results show thermal effects related to the use of three boundary conditions based on tissue-air convection and interfaces with prescribed temperatures. They highlight the interest of using a reflecting interface which allows to maintain the tissue surface temperature at a prescribed (and bearable) value, while reducing the laser power owing to a possible redistribution of light in front and within the tumor. Other results show that the thermal field profiles better fit the boundaries of the tumor when it is surrounded by a fat-engineered layer with a reduced thermal conductivity. For this given tissue configuration featured with a reflecting interface, tissue damage more localized in the tumor was observed with a less laser power required for the thermal treatment. These results provide a theoretical basis for future investigations.