Some Effects of Beam Thickness on Photon Migration in a Turbid Medium

Abstract We analyse the effects of extended rather than point optodes on several properties of photon migration in a turbid medium with internal absorption in a diffusion model suggested by a number of biomedical applications. The parameters considered include the surface flux of photons re-emitted back through the surface as a function of distance from the centre of the injecting optode, the surface intensity profile as a function of time for optodes separated by a fixed distance, and the distribution of the maximum depth reached by a photon, conditional on its being re-emitted through the interface at a variable distance from the injection point. Our major result is that the effects of extended optodes are much more significant when internal absorption is high.

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