Applications of the One-Dimensional Diffusion Approximation to Biological Tissue. (Reannouncement with New Availability Information).

摘要

Radiative transfer relates the macroscopic optical properties of a light scattering and absorbing material to microscopic parameters characterizing the individual particles, usually the absorption coefficient, total scattering coefficient, and mean cosine of the scattering angle. In densely scattering media the numerical values of these parameters must be calculated by fitting experimental quantities to theory, typically the transmission coefficient, reflection coefficient, and a third parameter such as the attenuation depth. Approximate radiative transfer theories have been employed to solve the 'inverse problem' for practical geometries. The recent review of Star et al. describes some mathematical models of current interest. The diffusion approximation treats light propagation in a turbid medium as equivalent to particle diffusion. However, recent measurements on animal tissues led to values of g close to unity. The purpose of the present work was to construct a diffuse optics spectrophotometer for measuring the optical properties of tissue layers over a wide spectral range and analyze the experimental results with two formulations of the one-dimensional diffusion approximation based on different angular scattering distributions or 'phase functions'.