Interaction of Pulsed Lasers andTissues in Tissue Treatments

• Main Authors: Sheng-Chi Lin, 林聖棋
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/35422621493480599523

碩士 === 國立中央大學 === 機械工程研究所 === 91 === The physical processes of laser-tissue interactions are investigated theoretically. The radiative transfer equation (RTE) is used to simulate the laser propagation in tissues. The model includes emission, absorption and anisotropic scattering mechanisms. The RTE is solved by using the discrete — ordinates method. The energy equation is solved by the control volume based finite different method. The resulting numerical code, written in Fortran, is validated by comparing the results with available experimental measurements. The effects of several important parameters on the coagulation and ablation depths of tissue are studied. Results show that the ablation depth increases with the incidence fluence. The pulse frequency of the laser has small influence on the ablation depth. On the other hand, the ablation depth is not affected by t he pulse duration. Laser energy lasers are also used in thermal treatment of skins. In this work, skins are separated into four layers, namely, stratum corneum, epidermis, dermis, and subcutaneous tissue. The results show that, under laser irradiation, the temperature difference between the skin surface and the dermis layer is very large. For better control of affected area, appropriate pulse duration should be used. For applications in photodynamic therapy (PDT), the energy distribution in tissue during the treatment period is investigated. Increasing the absorption coefficient of the tumor leads to higher energy density in the tumor region, this is beneficial fort PDT. The effective attenuation coefficient of the surrounding tissue has profound in influence on the treatment results.