@article{prahl91a,
  author = {S. A. Prahl},
  title = {Non-Invasive Quantification of Chromophores in Skin Using Reflection},
  journal = {Third Annual Meeting of the European Society for Pigment Cell Research},
  year = {1991 abstract only},
  abstract = {A method for determining chromophore concentrations in a scattering and absorbing material using reflectance spectroscopy is presented. The information provided by reflectance spectroscopy about the intrinsic absorption properties of skin is obscured by the scattering process. An algorthim based on radiative transport theory partially solves the scattering problem by (1) translating reflectance to ratios of the intrinsic absorption to the intrinsic scattering coefficient, (2) being accurate for all reflectance values, and (3) including the influence of internal reflection from the boundary in the calculations. \vskip2mm The wavelength dependence of the scattering coefficient of skin is relatively constant among individuals. Since the spectral dependence of scattering and of absorption by each chromophore is known, the ratios of absorption to scattering may be fit by varying the scattering magnitude and the chromophore concentrations. By using the entire visible spectrum to assess chromophore concentration, the method becomes less sensitive to minor reflectance fluctuations. Furthermore, this method can be applied to any added chromophore with known absorption properties which is present in sufficiently high concentrations to perturb the reflectance spectrum. \vskip2mm Experiments in scattering and absorbing agar phantoms are presented. The method is validated for moderate absorber concentrations when light scattering is comparable to that of skin. Optical properties obtained from in vitro skin samples show the spectral characteristics of scattering among individuals. Finally, in vivo reflection data from human skin is used to obtain concentrations of oxy-hemoglobin, deoxy-hemoglobin, beta-carotene, bilirubin, and melanin.},
}