Estimation of Melanin Concentration, Blood Concentration, and Oxygen Saturation in Skin Tissue Layers with Different Depths Unaffected by Shading

Measurement of melanin concentration, blood concentration and oxygen saturation in skin tissue is highly important technology in medical and cosmetic fields. Most previous studies neglect depth inhomogeneity of blood concentration distribution in skin tissue. However, skin tissue has a complex layered structure, and it is known that distribution of blood concentration differs greatly depending on the depth. Although a method has been proposed considering the inhomogeneity of blood distribution in depth direction, it is impossible to measure oxygen saturation. In addition, there is a limitation that shading influences the estimation as noise in any of the methods. Therefore, in this study, we propose a method to measure skin components concentration, which are melanin concentration, blood concentration, and oxygen saturation, in layers with different depths of skin tissue without influence of shading. First, to construct a dataset of absorbance corresponding to the skin components concentration we construct an optical multi-layered model of skin tissue and simulate light propagation and attenuation by light scattering and absorption with Monte Carlo simulation method. Each absorbance value is converted to a relative value based on an averaged absorbance value of all wavelengths to remove influence of shading. Next, we create a model describing an absorbance value corresponding to the skin components concentration with high dimensional multivariate regression based on the created dataset. This model enables to estimate the skin components concentration from spectral information without influence of shading. The proposed method is evaluated by simulation and shown to have state-of-the-art performance.