Comparison of melanin content of tiny moles versus normal skin sites using diffuse reflectance spectroscopy

摘要

Diffuse reflectance spectroscopy (DRS) has been widely used to interrogate the metabolic state and structure of several biological tissues with diagnostic purposes. The aim of this research is to compare the melanin content (melanosome volume fraction) of normal non-pigmented human skin sites versus skin sites containing tiny moles ranging from 1.2 mm to 2 mm diameter. The study was carried out in a group of ten volunteers presenting five different skin phototypes (I-V). Diffuse reflectance spectra of these sites were acquired with a USB 4000 fiber optic spectrometer and homemade optical probe consisting of two optical fibers separated 2.5 mm. In order to extract optical properties of skin sites containing tiny moles, a relative simple but novel skin model was proposed and used in combination with a slightly modified version of the inversion algorithm analyze2.m which is freely available. We found that melanin content ranges from 3.3 % to 29.2 % for the normal skin sites surrounding pigmented skin sites, while for skin sites with tiny moles melanin content varies from 7.6 % to 78.4 %. Our finding shows that for each volunteer the melanin content of pigmented areas is twice or more the melanin content of non-pigmented normal skin areas. In addition, we have evaluated the sensibility of the inverse extraction algorithm when the melanin content is varied while the remaining "guess parameters" (S, B, a, const) are kept constant. We have found that all the remaining parameters are strongly affected when the melanin content is changed.