Determination of reduced scattering and absorption coefficients by a single charge-coupled-device array measurement, part II: measurements on biological tissues

The optical properties of various biological tissues have been investigated by the measurement of the maximum intensity M and the full width at half maximum (FWHM) of the intensity profile of a scattered light beam. These two quantities have turned out to be highly discriminating parameters for the different tissues under scrutiny: muscle, liver, adipose, and gray and white brain matter. The inverse problem, i.e., the computation of the absorption and reduced scattering coefficients from M and FWHM, has been solved in the domains where Monte Carlo simulations have yielded possible values for M and FWHM. The accuracy is typically 5% for the reduced scattering coefficient and 20% for the absorption coefficient. This method is judged to be reasonably good for application to biological materials: it allows a good overall characterization of tissues. A scanning technique has been developed to evaluate the variability of the optical parameters at different locations in biological tissues. Whereas Monte Carlo simulation works well for tissues such as muscle or liver, it appears to be inappropriate in describing the optical properties of adipose and brain tissues. The reasons are still unclear and are probably related to the particular structural properties of such tissues.