Improved accuracy of frequency-domain photon migration close to light source using delta–P1 approximation of the adjustable parameter f

Abstract

The δ–P1 approximation can improve the accuracy of the diffusion equation in the near field. Usually, the method to determine the fractional forward-scattering peak f in the δ–P1 approximation is to compare the first two moments of the Henyey–Greenstein phase function and those of the δ–Eddington phase function. The error relative to Monte Carlo estimation still exists within a mean free path using the value f above. To overcome this defect, we put forward a new method to determine the parameter f for improving the accuracy of frequency-domain photon migration in the δ–P1 approximation if the detector is close to a light source. Results demonstrate that the adjustable f δ–P1 approximation can accurately predict photon fluence rate at distances less than half the transport mean free paths from the source.