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.
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