Numerical Simulation and Experimental Study on Thermal Damage Process in Tissue during High-Intensity Laser Irradiation

Various phase-changing thermal effects, i.e. evaporization, carbonization and melting, occur sequentially in the biological tissue irradiated by high-intensity laser. According to this practical thermal effect, a new heat transfer model for laser-tissue thermal interaction is proposed. In the model two heterogeneous tissues, i.e. carbonization layer and bio-tissue layer, are considered and two different phase-changing interfaces are introduced. Some parameters such as the temperature and moving velocity on the interfaces as well as the carbonization depth are obtained by numerical solution. The relationship between these parameters and the laser power density is studied. Numerical simulation shows that the laser-tissue thermal interaction model has two stages: the initial non-steady stage and the succeeding quasi-steady stage with the characteristic of constant parameters such as interface temperature, interface moving rate and carbonization zone etc. Some laser-tissue thermal damage experimental results are presented and discussed by contrast with the mathematical simulation results. The predicted carbonized depth and thermal damage depth coincide well with experimental observations.