Vertex/propagator model for least-scattered photons traversing a turbid medium

The least-scattered photons that arrive at a detector through highly scatte ring tissues have the potential to image internal structures, functions, an d status with high imaging resolution. In contrast, optical diffusing tomog raphy is based on the use of the late-arriving photons, which have been dif fusely scattered, leading to very low imaging resolution. A good model of t he early-arriving photons, i.e., the least-scattered photons, may have a si gnificant effect on the development of imaging algorithms and a further und erstanding of imaging mechanisms within current high-resolution optical-ima ging techniques. We describe a vertex/propagator approach that attempts to find the probabilities for least-scattered photons traversing a scattering medium, based on analytical expressions for photon histories. The basic mat hematical derivations for the model are outlined, and the results are discu ssed and found to be in very good agreement with those from the Monte Carlo simulations. (C) 2001 Optical Society of America.