Time-resolved reflectance for the evaluation of tissue optical properties

The analysis of the time-resolved reflectance curve allows the simoultaneous determination of the absorption and scattering coefficients. A system for time resolved reflectance measurements was developed. It is based on a mode-locked dye laser and on electronic chain for time-correlated single photon counting. Fiber optics are used for both illumination and collection. The system response is characterized by a FWHM < 60 ps tipically. The diffusion theory provides a theoretical model for the interpretation of the experimental data. The performances of the instrumentation are excellent with respect to both linearity and accuracy, as proved by measurements carried out on tissue phantoms. Finally, different tissue types were characterized in vitro and the optical parameters of human hand palm were evaluated in vivo.