Simulações de Monte Carlo para estudar a propagação da luz através da pele de diferentes fototipos

Abstract

In the last years, there has been an increase in interest in using light as a treatment, and it has been shown that this is a great alternative to more traditional treatments. Due to the complex nature of photons, it is important to consider the many characteristics of the tissue because every interaction will affect the photons in some way; so it is important to understand how these characteristics affect how a photon interacts with the tissue and if it has any negative effects on the treatment. In this study, we investigated how different melanin concentration affects the propagation of light inside the tissue. A six-layer tissue was created using pymcx, a Python interface for Monte Carlo Extreme; the tissue model was adapted from LaRochelle et al.(1), but the first layer was disregarded due to being too thin and having a low absorption coefficient. The optical properties were obtained by LaRochelle et al.(1), only the absorption coefficient of the living epidermis that was calculated using the wavelength, concentration of melanin, eumelanin pheomelanin ratio, and other parameters. In our simulation, we varied the melanin concentration from 0% to 50% to include all phototypes previewed in the Fitzpatrick scale, and we also evaluated the effects in four different wavelengths, being 410 nm, 630 nm, 780 nm, 850 nm. With analysis of the results we were able to see a significant difference in the light propagation, as in higher melanin concentrations the lower intensity in deeper layers, this effect is even more valuable in higher wavelengths due to its “penetration power”. We believe that by increasing the melanin concentration, the living epidermis absorption coefficient increase, thus absorbing more energy in the first layer, leaving less energy available to deeper ones.