Simulation of Temperature Distributions in Tissue Upon Laser Pulse Irradiation Including Water Mass Transfer

Lasers, due to their unique characteristics, have tremendous applications in the medical field. Generally all laser applications in hie-medicine involve the propagation of laser energy through tissue. Energy is deposited giving rise to many physical, hie-chemical, and mechanical effects. Among these are dynamical changes in the local temperature distributions within the tissue. Analysis of the temperature changes requires the creation of an appropriate optical transmission and heat flow model that incorporates user specified laser parameters. Here, a numerical simulation model was developed to study both steady state and time dependent temperature distributions due to pulsed laser radiation within user specified heterogeneous bio­ tissues. Several physical aspects such as the role of water evaporation and diffusion due to excessive localized heating were included in the fonnalism for the spatial tissue temperature distributions. This model was first implemented numerically for a one-dimensional (ID) tissue geometry and later extended to cylindrically symmetric two-dimensional geometries. This work used the Pennes' bio-heat equation and the Crank-Nicholson implicit finite difference method for solving the system of equations. Time and spatially pendent temperatures were successfully obtained and form the basis for the evaluation of other hie-effects such as tissue necrosis and ablation. Various simulation results and test cases of time-dependent tissue temperature distributions with inclusion of water diffusion and evaporation, are presented in this thesis research.