Noninvasive Detection of the Skin Structure and Inversed Retrieval of Chromophore Information Based on Diffuse Reflectance Spectroscopy.

The detection of skin's structure lays the foundation for personalized laser surgery of vascular skin disease, which can be noninvasively achieved by diffuse reflectance spectroscopy (DRS). A two-step inverse Monte Carlo radiation method based on DRS under two source-detector separations was proposed to quantify the skin structure, including chromophore concentration (melanin f _m and hemoglobin f _b), epidermal thickness t _epi, average vessel diameter D _ves, depth d _pws and thickness t _pws of the vascular layer for diseased skin. The method fitted the simulated DRS to the measured DRS iteratively, differences between which were described by a specific objective function to amplify blood absorption at 500-600 nm, and D _ves, d _pws, and t _pws were estimated based on f _m, f _b, and t _pws fitted in the first step. The results showed that the two-step method dramatically improve the inversion accuracy with mean errors of f _m, f _b, t _pws, and d _pws less than 5%.