Reconstruction of in vivo skin autofluorescence spectrum from microscopic properties by Monte Carlo simulation.

The in vivo skin autofluorescence spectrum was reconstructed by Monte Carlo simulation using microscopic fluorophore distributions and intrinsic fluorescence spectra measured from excised skin tissue sections as well as employing published skin tissue optical parameters. The theoretical modeling took into account the light-tissue interactions of scattering, absorption, and regeneration of fluorescence photons. The modification of the intrinsic spectra by tissue optical properties to generate the in vivo spectrum observed at the tissue surface can be represented by a fluorescence detection efficiency function (eta) which equals the integral of the product of the excitation light distribution inside the tissue and the fluorescence escape efficiency. Comparison of the reconstructed in vivo spectrum with the measured spectra showed good agreement, outside of the blood absorption bands, suggesting that (i) the theoretical modeling, (ii) the skin optical parameters used, and (iii) the measured microscopic morphology and spectral data are consistent. The divergence which exists over the strong blood absorption wavelength band (530-600 nm) suggests that the effect of blood contents on in vivo tissue optical properties deserves further investigations.