强激光对组织热损伤过程的数值模拟与实验研究

强激光作用于生物组织时会产生气化、碳化和熔融等相变热效应，并对组织造成热损伤，据此提出了包含碳化层和生物组织层双层结构、具有两个相间移动边界的激光与生物组织热相互作用数学模型。对数学模型进行了数值求解，得出了组织内部的温度分布，相间边界的温度，相间边界移动速度及碳化层厚度等参数的变化规律，并探讨了它们与激光强度之间的相互关系等问题。数值模拟表明，该光热作用过程分为两个不同阶段：起初的非稳态阶段以及紧接着的准稳态阶段，此时相间边界温度、相间边界移动速度以及碳化层的厚度均为与时间无关的常数。进行了激光生物组织热损伤实验，实验结果与数值模拟结果进行了比较和分析。结果表明，热损伤区大小、碳化层厚度等模拟值能与实验值较好地相符。

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.