Photon migration in turbid media: a finite-element solution for the most favorable path

Abstract

A better understanding of the fundamental principles of photon migration in highly scattering media is of great importance for developing new methods for disease diagnosis, imaging, and tomography. In this paper we present a most-favorable-path approach to the problem of light propagation in turbid media, based on the diffusion equation. The most favorable path, on which photons will be found, can be obtained from the path of the net flux propagation. The diffusion intensity and the direction of the net flux can be calculated with the finite-element method, which can deal with heterogeneous problems and frequency-domain problems within complex geometry, and can introduce boundary effects as well. Simulations were conducted for phantoms with different optical parameters and source-detector separations. Experiments have been performed to verify this new method. The most favorable path is found to be more sensitive to the source-detector separation and the absorption coefficient of the medium than to the scattering coefficient. The feasibility of using the theory in optical tomography for the recognition of objects hidden in turbid media is discussed.