Simulation And Experimental Monitoring Of Temperature Field In Laser-induced Interstitial Thermotherapy

As one of the most serious diseases with high morbidity and fatality rate in the world,liver tumors have always been the focus of attention and research by domestic and foreign scholars.Laser-induced interstitial thermotherapy which is a minimally invasive surgical method has been widely used in treatment of liver tumors because of its low cost,satisfying efficacy,quick recovery and minimal invasiveness.It causes the tissue necrosis through the interaction of light and heat effects when tissue absorbs the energy of laser.However,it is noteworthy that the heat in the tumor area will be transmitted to the normal tissues around the tumor by the heat conduction.Therefore,if the laser dose is too large,not only the tumor tissue will be ablated,but also the normal tissue will be damaged.To avoid this result,real-time temperature monitoring of the tissue during laser-induced interstitial thermotherapy is required.In this paper,the finite edement simulation and the vitro experiment are compared to provide the theoretical basis for the best clinical individual dosage control.The main work of this study is as follows:1)Based on the transmission theory of the light in the tissue,heat conduction theory and heat damage theory,this paper carried on finite element simulation research during laser treatment.Two sets of temperature distribution were simulated by two different tissue heat transfer theory which were the pennes bioheat transfer equation and the hyperbolic bioheat transfer equation respectively.Then,the results were compared and analyzed.The results showed that compared with the results obtained by Pennes equation,the temperatures obtained by Hyperbolic equation increased slowly before two temperature series intersected,and then increased quickly.And,the distance of maximum damage area between two equations was close to 13.1%.2)By introducing dynamic optical parameters during simulation of tissue damage process,we proved that the change of parameters with tissue temperature would have an impact on the results.3)By adding large blood vessels during simulation of tissue damage process,we found that the tissue temperature in the vicinity of the large blood vessel was significantly lower than that of the blood vessel-free tissue and the perfusion rate also affected the results.4)By vitro porcine liver experiment,we found that Hyperbolic method was superior to Pennes method and also validated the feasibility of hyperbolic bioheat transfer equation in laser-induced interstitial thermotherapy.The main creativeness of this study is as follows:1)The hyperbolic bioheat transfer equation was introduced into the simulation of LITT and the validity of the equation was verified through quantitative calculation.It would be the theoretical basis for using hyperbolic bioheat transfer equation to solve more complicated tissue temperature field in the future.2)In the simulation,the dynamic change of optical parameters with temperature was considered to further improve the simulation accuracy.3)In the simulation,the model of large blood vessel tumor was considered to propose that blood vessels and blood flow velocity would have a significant impact on the tissue temperature.It provided a theoretical basis for in vivo experiments.