The determination of in vivo human tissue optical properties and absolute chromophore concentrations using spatially resolved steady-state diffuse reflectance spectroscopy

A method is described for measuring optical properties and deriving chromop hore concentrations from diffuse reflection measurements at the surface of a turbid medium. The method uses a diffusion approximation model for the di ffuse reflectance, in combination with models for the absorption and scatte ring coefficients. An optical fibre-based set-up, capable of measuring nine spectra from 400 to 1050 nm simultaneously, is used to test the method exp erimentally. Results of the analyses of phantom and in vivo measurements ar e presented. These demonstrate that in the wavelength range from 600 to 900 nm, tissue scattering can be described as a simple power dependence of the wavelength and that the tissue absorption can be accurately described by t he addition of water, oxy- and deoxyhaemoglobin absorption.