Control Light Delivery in PDT by Taking Account the Optical Properties of Hair Density on the Skin Surface

Information concerning energy deposition during laser therapy of skin is needed to comprehend and asses the results of clinical procedures in dermatology. The prupose of this study is to show an optical model that predicts infection dose for the skins in different hair density and which can be used to explore whether parameteres of hair on the skin surface, merited the bio optical sudies and phsician during irradiation. A skin optic study by the advanced system analysis program (ASAP) software represents the best way for improving investigation of light propagation into the skin. The ASAP technique of the skin modeling is the process of constructing optical objects, such as a set of skin layers and propagation of a laser beam, whose behavior or properties correspond in some way to a particular real-wold system. The results showed that, hair on the skin surface minimized dose injection of the skin target during the PDT procedure. The differences in penetrating injection dose for layers of skin between low and high hair densities after irradiation, for end epidermis layer at 0.098 mm in the skin region with high and low hair density are 832.1 mW.mm-3 and 853 mW.mm-3 respectively, but for skin without hair is mW.mm-3. Using this resutl, we found that the region of decreased light fluence rate that formed at the epidermis layer significantly reduces the power uptake in deep layers. Moreover, hair density on the skin surface precents light penetration into the deeper region. Therefore, if the hair parameters are ignored, a relatively significant effect of the dose rise occurs in a deeper area resulting great influence in depth of target.