Influence of the scattering phase function approximation on the optical properties of blood determined from the integrating sphere measurements.

We investigated the impact of the scattering phase function approximation on the optical properties of whole human blood determined from integrating sphere measurements using an inverse Monte Carlo technique. The diffuse reflectance Rd and the total transmittance Tt(λ=633 nm) of whole blood samples (Hct=38%) were measured with double-integrating sphere equipment. The scattering phase functions of highly diluted blood samples (Hct=0.1%) were measured using a goniophotometer. We approximated the experimentally determined scattering phase functions with either Henyey-Greenstein (HGPF), Gegenbauer kernel (GKPF), or Mie (MPF) phase functions to preset the anisotropy factor μ¯ for the inverse problem. We have employed HGPF, GKPF, and MPF approximations in the inverse Monte Carlo procedure to derive the absorption coefficient μa and the scattering coefficient μs. To evaluate the obtained data, we calculated the angular distributions of scattered light for optically thick samples and compared the results with goniophotometric measurements. The data presented in this study demonstrate that the employed approximation of the scattering phase function can have a substantial impact on the derived values of μs and μ¯, while μa and the reduced scattering coefficient μs' are much less sensitive to the exact form of the scattering phase function. © 1999 Society of Photo-Optical Instrumentation Engineers.