Thermo-mechanical laser ablation of soft biological tissue: modeling the micro-explosions

Characteristics of thermo-mechanical laser ablation process are investigate d using an original numerical model. In contrast with previous models, it i s based on a microscopic physical model of the micro-explosion process, whi ch combines thermodynamic behavior of tissue water with elastic response of the solid tissue components. Diffusion of dissipated heat is treated in on e dimension, and the amount of thermal damage is assessed using the Arrheni us model of the protein denaturation kinetics. Influence of the pulse fluen ce and duration on temperature profile development, ablation threshold, and depth of thermal damage is analyzed for the case of Er:YAG laser irradiati on of human skin. Influence of mechanical properties on the ablation thresh old of soft tissue is predicted theoretically for the first time. In additi on, feasibility of deep tissue coagulation with a repetitively pulsed Er:YA G laser is indicated from the model.