A comparison between transport and diffusion calculations using a finite element-spherical harmonics radiation transport method

• Published in: Medical physics (Lancaster) 2002-09, Vol.29 (9), p.2013-2023
• Main Authors: Aydin, E. D., de Oliveira, C. R. E., Goddard, A. J. H.
• Format: Article
• Language: English
• Subjects: anisotropic media; anisotropic scattering; Anisotropy; biological tissues; bio‐optics; Boltzmann equation; Boltzmann transport equation; Brain - anatomy & histology; Brain - radiation effects; Brain Neoplasms - diagnosis; Cerebrospinal Fluid - radiation effects; Computer Simulation; Diffusion; Diffusion Magnetic Resonance Imaging - methods; Drug delivery; Finite Element Analysis; finite elements; Finite‐element and Galerkin methods; Head - anatomy & histology; Head - radiation effects; Humans; Image Enhancement - methods; Light; light propagation; Models, Biological; Numerical modeling; Optical/infrared radiation effects; Phantoms, Imaging; Photon absorption; photon migration; Photon scattering; photon transport theory; Photons; Researchers; Scattering, Radiation; Skin - anatomy & histology; Skin - radiation effects; spherical harmonics; Subarachnoid Space - anatomy & histology; Subarachnoid Space - radiation effects; Tissues; Transport processes; Visual imaging
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.1500404

Most researchers choose the diffusion approximation to the transport equation as the model to describe photon migration in biological tissues. However, the applicability of this approximation is limited and, in certain cases, invalid. In this paper we introduce a two-dimensional, finite element-spherical harmonics (FE- P N ) radiation transport method for the simulation of light propagation in tissue. The propagation of light is investigated first in a layered cylinder, which can be seen as a very simplistic approximation of a human head. Effects of the anisotropy factor g on the photon migration is then examined in homogeneous and heterogeneous media for different values of g and μ s . The influence of void-like heterogeneities and channels in which absorption and scattering are very small compared with the surrounding medium on the transport of photons is also investigated. Significant differences between transport and diffusion calculations are shown to occur in all cases.