Research on thermal influence of laser radiation on skin with non-trivial geometry

Usually biological tissue has complex geometry. In earlier works we used simple skin model with a number of horizontal layers. In this work we use the model that approximates complex objects. For example, cancerous growth consists of many layers which can be of different forms, for inter alia blood vessels. In this work we attempted to elaborate a mathematical model of thermal response of laser irradiated multilayered biological tissue. Every layer has its own optical and physical characteristics. We used Monte-Carlo simulation to calculate the propagation of light (laser beams) in tissue and receive the heat source function. As we usually have radial symmetric laser beams we use cylindrical coordinates. The solution of the 2D heat conduction equation is based on finite-element theory with the use a predefined number of finite elements. We simulated constant and pulse laser irradiation and as result there are temperature fields and the dynamics of heat conduction. Analysis of the results shows that heat is not localized on the surface, but is collected inside the tissue. By varying the boundary condition on the surface and type of laser irradiation (constant or pulse) we can reach high temperature inside the tissue without simultaneous formation of necrosis.