Comparison of spatial differencing schemes for the equation of radiative transfer applied to biomedical tissues

When numerically implementing the equation of radiative transfer (ERT) to calculate light propagation in biological tissue, one has several choices on how to perform the spatial discretization. In this study we investigate the performance of two commonly employed differencing schemes ("step" and "weighted diamond"). Using a discrete-ordinates finite-volume method in a two-dimensional absorbing and scattering medium, the code performances are evaluated in terms of accuracy and computational requirement. We find that, compared to the step-differencing scheme, the weighted diamond differencing scheme provides more accurate solutions of the radiation intensity over a wide range of optical properties. Furthermore, the weighted diamond scheme is computationally more efficient than the step method. When used in conjunction with tomographic reconstruction algorithms, we observe that using the weighted-diamond differencing scheme leads to more accurate reconstructions of the optical properties.