Retrieval of the physiological state of human skin from UV–Vis reflectance spectra – A feasibility study

We test the feasibility of using an accurate radiative transfer model for the coupled air–tissue system in conjunction with a classic inversion scheme based on Bayesian optimal estimation theory for retrieval of parameters describing the physiological state of human skin. To that end, we analyse ultraviolet and visible reflectance spectra from human skin measured before, immediately after, and on each day for two weeks after photodynamic treatment with the hexyl ester of ALA and exposure to red light (632 nm). For the first time, we show that it is possible to perform a simultaneous retrieval of the melanosome concentration in both the basal and the upper layers of the epidermis.