An Analysis of Interaction between laser Light and Biological Tissue using Computer Simulation

Abstract

Recently Nd: YAG laser is used clinically for the purpose of hemostasis and coagulation. To know the temperature distribution in the tissue, at which Nd: YAG laser was irradiated to the tissue, is important as to determine irradiation time and power. Then we simulated the temperature distribution in the tissue as to CW and repeated pulse irradiation by computer when Nd: YAG laser was irradiated to the tissue. Power density of laser in the tissue was calculated as the sum of direct beam and internal beam (scattered beam). Power density by internal scattering with higher order scattering (third order) was calculated. At the method of numerical analysis which used the 2-dimension heat conduction equation with heat source term of power density. At repeated pulse irradiation, the rise of temperature was calculated from the power density is time of pulse duration, and in time of pulse interval the temperature distribution was calculated by the method of numerical analysis which was used the 2-dimensional heat conduction equation without heat source of power density. Two beam modes (Gaussian and rectangular profile) were used to calculate the rise of temperature in the tissue. Each two combinations were analysed and discussed.