Coupling between radiative transport and diffusion approximation for enhanced near-field photon-migration modeling based on transient photon kinetics

Abstract

Coupling between transport theory and its diffusion approximation in subdomain-based hybrid models for enhanced description of near-field photon-migration can be computationally complex, or even physically inaccurate. We report on a physically consistent coupling method that links the transport and diffusion physics of the photons according to transient photon kinetics, where distribution of the fully diffusive photons at a transition time is provided by a computation- saving auxiliary time-domain diffusion solution. This serves as a complementary or complete isotropic source of the temporally integrated transport equation over the early stage and the diffusion equation over the late stage, respectively, fromwhich the early and late photodensities can be acquired independently and summed up to achieve steady-state modeling of the whole transport process. The proposed scheme is validated with numerical simulations for a cubic geometry.

Time-Domain Near-Infrared Spectroscopy and Imaging: A Review

“…Software for the two-layered finite cylinders is given in the Reference [32] (pp. [109][110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125].…”

“…In the fields of DOT and fluorescence diffuse optical tomography (FT) for small animals and small organs like human fingers and teeth, the early-time regime plays an important role, and simple application of the DE may be inappropriate. Several hybrid models have been proposed for CW [116], FD [117,118], and TD [119][120][121]. In the FD version of the coupled RTE-DE model [117], the whole computation domain is divided into two subdomains of near-field regions using the RTE and far-field regions using the DE, and the continuity of the intensity and its derivatives at the interface between the two subdomains are given for connecting the solutions of the RTE and DE.…”

“…Zucchelli et al and Re et al utilized the analytical formulations of the partial pathlength of Equation (24) with the analytical solutions of the TD-DE for two-layered media to estimate perturbations of µ a2 [32] (pp. [109][110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125] [152,153]. When the spectroscopic TR reflectance, R(t, λ), is divided into many time gates, the ratio of the perturbed and unperturbed R(t, λ) averaged over the g-th time-gate is derived from Equation (24) as,…”