Effects of scattering and absorbing medium in the fluorescence conversion efficiency of physical tissue models

Auto-fluorescence spectroscopy based on spectral line shape and intensity has been in use as a promising technique for detecting varying degrees of tissue malignancy. Tissue is a turbid medium with multi-layered structure constituting of different fluorophores, absorbers and scattering molecules. Tumor progression in tissues is ac-companied by varying degrees of biochemical and morphological changes. These include changes in nuclear size and density, epithelial thickness and increase in the hemoglobin (Hb) concentration associated with changes in metabolic activity. These variations in overall tissue scattering and absorption properties in turn modulate the fluorescence spectrum emitted and derived from tissues. Estimation of fluorescence conversion efficiency in the turbid tissue needs to take into account these effects of absorption and scattering in order to be evolved as a parameter for tissue discrimination. In this study, we set to investigate the factors affecting tissue fluorescence conversion efficiency by making use of physical models of the tissue. Liquid tissue models were prepared with different concentrations of absorbing and scattering media to simulate biological tissues of various degrees of malignancy. The results indicate that emitted fluorescence from the tissue model is subjected to variations by multiple scattering events and absorption. The fluorescence conversion efficiency of the models were derived and correlated to the experimental results with possible diagnostic significance.