Melanin absorption spectroscopy: new method for noninvasive skin investigation and melanoma detection

Abstract

We present a new method for studying melanin in vivo based on diffuse reflectance spectroscopy of human skin. We find that the optical absorption spectrum of in vivo melanin exhibits an exponential dependence on wavelength, consistent with, but with a higher decay slope than, in vitro results. We offer theoretical justification for this exponential dependence on the basis of a recently proposed model for the structure of eumelanin protomolecules. Moreover, we report on a new method for analysis of diffuse reflectance spectra, which identifies intrinsic differences in absorption spectra between malignant melanoma and dysplastic nevi in vivo. These preliminary results are confirmed both by analysis of our own clinical data as well as by analysis of data from three independent, previously published studies. In particular, we find evidence that the histologic transition from dysplastic nevi to melanoma in situ and then to malignant melanoma is reflected in the melanin absorption spectra. Our results are very promising for the development of techniques for the noninvasive detection of melanoma and, more generally, for the study and characterization of pigmented skin lesions. It is also a promising approach for a better understanding of the biological role, structure, and function of melanin.

Simple and accurate expressions for diffuse reflectance of semi-infinite and two-layer absorbing and scattering media

“…It has been applied to non-invasive health-monitoring of in-vivo biological tissues [1][2][3][4][5][6][7], quality control in agricultural applications [8][9][10][11][12], and remote terrestrial sensing [13][14][15][16], for example. In many biological applications, the irradiated medium can be modeled as a strongly scattering multilayer medium whose radiative properties are constant within each layer but differ from layer to layer.…”

Rapid and accurate estimation of blood saturation, melanin content, and epidermis thickness from spectral diffuse reflectance

“…Diffuse reflectance spectroscopy has found many applications in non-invasive monitoring of biological tissues [1][2][3][4][5][6][7]. This technique investigates tissue structure, chromophore concentration, and health by measuring the tissue's optical properties.…”

Non-Invasive Optical Method for Epidermal Thickness Estimation

“…Each subject is displayed in a different color and each finger is represented with numbers from 1 to 5. A percentage of the transmitted light is absorbed due to the content of melanin in the epidermis (Zonios et al, 2008). Human skin colors are primarily due the presence of melanin in the skin (Alaluf et al, 2002).…”