Effects of Sources, Boundaries, and Heterogeneities on Photon Migration

Abstract

This paper considers three issues regarding the suitability of diffusion theory for calculations of photon density waves: (1) Directed sources, such as a collimated beam, (2) Boundaries (eg., an air/tissue interface), and (3) Heterogeneities (eg., tumor or vessel). Heterogeneities have optical properties of absorption (µa) and scattering (µs' = µs(1-g)) in [cm-1] which differ from the surrounding background tissue properties, and are treated by a method of superposition of virtual sources (the SVS Method).