The effects on the tissue temperature distribution of low-intensity laser irradiation

Temperature is a long established indicator of health. With the advancement of clinical medicine in thermal disease diagnostics, understanding the thermal life phenomena and temperature behavior has become increasingly important. The biological effects of human exposure to low-intensity laser irradiation thermo-therapy, the best established are those due to elevation of tissue temperature. Bio-heat equations (BHEs) are necessary for predicting tissue temperature during thermal treatment. To prevent harmful levels of heating, restrictions have been proposed on low-intensity laser irradiation as the external spatial heating. In this paper, considering the different properties for the pathological tissue and the normal tissue, using a numerical method to solve the Pennes' bio-heat equation, we analyzed theoretically the relationship between the temperature distribution and external spatial heating during low-intensity laser irradiation. The effects of the thermal parameters such as the heat conductivity, blood perfusion rate, and metabolic rate of the tissues on the temperature distribution were discussed. The results can be used to predicted different effects on the temperature variation and distribution, the thermal damage distribution and the thermal damage volume etc. The results are also useful in optimizing the therapeutic parameters for improved low-intensity laser irradiation treatments and for better understanding the thermal life phenomena in living tissues.