Light Transport in Tissue |
IntroductionThis chapter describes the delta-Eddington approximation to the radiative transport equation. In Section 4.1 the diffusion equation is derived from the transport equation; this derivation follows that of [30] with the exception that the Eddington phase function has been replaced by the delta-Eddington phase function of Joseph et al. [34]. New boundary conditions required for a number of different physical situations are derived in Section 4.1. The results of the previous sections are converted into dimensionless units in Section 4.2. The one-dimensional diffusion equation is solved analytically in Section 4.3, and in Section 4.4 the calculation of flux, reflection, and transmission is discussed. The three-dimensional cylindrically symmetric solution to the diffusion equation is presented in Section 4.5. In Section 4.6 the solutions obtained using the diffusion approximation are compared with exact solutions obtained with the adding-doubling method.
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