Selective Photothermolysis And Photonics Therapy Of Skin And Its Thermal Damage Evaluation Method & Technology

The goal of this dissertation, after reviewing the history and development of selective photothermolysis of skin, was to improve the safety and efficacy of skin lesion light treatment, and devoted to several key issues as below.Firstly, the surface temperatures evolving with time of the Asian skin in vivo, which were irradiated by 532 nm pulsed laser, were measured using thermal camera. The results showed that the maximum skin surface temperatures of individual are different even under the same light irradiation parameters, so the choice of light treatment parameters should be based on individual. The optical absorption coefficients of individual Asian epidermis were deduced based on pulsed photothermal radiometry.Secondly, the important role of skin cooling in skin lesion light treatment was discussed. The temperatures of skin surface and in skin were measured using thermalcouples and numerically simulated. The role of precooling before laser irradiation, parallel cooling during laser irradiation and postcooling after laser irradiation were also analyzed. The results showed that skin cooling could improve radiant exposure and protect epidermis.Thirdly, the light distribution and temperature profiles in skin with lesion such as leg veins, photoaging skin, which were irradiated by pulsed laser, were numerically simulated using Monte Carlo in combination with finite difference method, and the thermal damage of skin was calculated based on Arrhenius rate process. The role of irradiation parameters such as wavelength, spot diameter, pulse duration and radiant exposure in improving light treatment efficacy was also discussed.Finally, the thermal damage of mouse skin irradiated by 1064 nm pulsed laser was evaluated. The skin images of TPEF/SHG were acquired using multiphoton microscopy, and the intensity of TPEF and SHG was also measured. The results showed that the intensity rate of SHG to TPEF was quantitatively consistent with the radiant exposure, and could be used to represent the extent of skin photothermal damage.