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

Abstract

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

Light source distribution and scattering phase function influence light transport in diffuse multi-layered media

“…In this last case, the specular and diffuse light coming from the location of the light source which illuminates the skin surface are studied with respect to different observation angles. The effects of the light source shape [23][24][25], surface roughness [26], optical-clearing [27] and hair density [28] on the photon dose absorbed in the human skin have been well investigated. However, to our knowledge, the influence of the angular distribution of the light source (ballistic, diffuse or Lambertian) on (θ 0 ) exponentiated cosine distribution function p b (z) distribution of ballistic light source along depth z p IsoForw (z) distribution of diffuse light source along depth z ω 0 source radius r s spherical radius θ angular deviation ρ radial distance z axial distance (depth) θ 0 angle defined only at the surface (x c , y c , z c ) coordinates related to the half-sphere geometry the light transport in the human skin structure has not yet been reported.…”