A Note on the Theory of Backscattering of Light by Living Tissue

A set of equations derived to describe the optics of highly scattering materials are explained, extended, and applied to the problem of in vitro and in vivo measurement of the relative oxygen saturation of nonhemolyzed blood. Fundamental absorption and scattering coefficients are described and related to the absorption coefficient of hemolyzed blood. Diffusion equations for light photons are used to solve the scattering problem in a three-dimensional system that may be useful for in vivo oxyhemoglobin measurements. Crude application to published data from in vitro measurements on nonhemolyzed blood indicates that the scattering coefficient of whole blood is probably not very wavelength-dependent.