Comparison of some Methods for Noninvasive Diagnostics of Human Skin Parameters by Scattered Light

The possibility of determining the structural and biophysical parameters of skin from the spectra of scattered light is assessed. Schemes for measurement of the coefficient of diffuse reflection, the coefficient of brightness back-scattered by biological tissue, and the spatial illumination at some distance from the source are examined. Algorithms are proposed for establishing the volume concentrations of melanine and blood vessels, the thickness of the epidermis, the degree of oxygenation of the blood, and the average diameter of the capillaries. It is shown that the first two schemes give approximately identical characteristics for solution of the inverse problem, although the polarization measurements are somewhat less susceptible to experimental error. Analysis of such similarity has demonstrated that it is due to features of the optical characteristics of the skin layers. The preferred method is the third experimental scheme, which is not subject of error and has substantially higher sensitivity to the degree of oxygenation of the blood and the average diameter of the capillaries and makes it possible to establish all the desired parameters of the skin with acceptable accuracy for practical purposes.