A local rapid temperature rise model for analyzing the effects of irradiation on human skin in laser treatments

In laser treatments, the difference in patient's degree of skin pigmentation is an important factor that can lead to medical accidents. However, the conventional heat transfer model is not available to analyze the effect of degree of pigmentation on the laser treatments. Therefore, we propose a new microscopic radiation heat transfer model that takes into account the point heat sources for the laser treatments. In the proposed model, skin considered as a bulk medium consisting of two layers, namely normal and pigmentation layers with the latter containing a larger number of melanosomes having a specific volume fraction (f_v,mel) as the degree of pigmentation. Using the proposed model, it was found that the distribution of the absorbed laser energy and temperature rise of the skin tissue is affected by the degree of pigmentation. When f_v,mel is high, the absorbed energy per single melanosome and thus the temperature rise of the pigmentation layer is lower than that in the deeper skin tissue. It was also shown that depending on f_v,mel, the distance between melanosomes decreases. When f_v,mel is high, the temperature of skin tissue between melanosomes increases.