Influence of hair color on photodynamic dose activation in PDT for scalp diseases

Abstract

In this study, an attempt has been made to differentiate between photodynamic dose for the persons with various color hairs by analyzing a hair parameter of light reflected from the skin surface and epidermis by absorption and scattering with chromophore. Furthermore, the purpose of this study was to show the effect of hair color and laser in skin during PDT, and to interpret changing in the light transmission ratio with blonde, light brown and black hair. In this study, engineering system software was advanced systems analysis program (ASAP) used to create realistic skin model and analysis the data. Three models of scalp skin were used; a scalp skin with blonde, light brown and black hair. The light transmitted through the skin sample, and the incident light was detected with a voxel element. The effect of optical characteristics of the hairs, such as hair color on PDT procedure is demonstrated. Results indicate that absorbing of the light due to the hair reduces the values of the fluence rate and light transmission, and is related to these characteristics of hair and melanin concentration in each type of hair. The model predicts that black hair got minimum fluence rate than light brown and blonde hair on the skin surface. It concluded that the hair parameter absorbing is one of the important features to take into account when evaluating dose. Therefore, a new method for dose evaluation from skin curves is proposed for PDT procedure. Additionally, we present the general model for light scattering, showing that the scattering by skin surface of different penetration depth, and the scattering and absorption processes by the hair's interior, affect the interaction of the laser and photosensitizer into the tissue. © 2011 Springer-Verlag.