Random walk analysis of time-resolved transillumination measurements in optical imaging

Data relating photon migration in human tissue can be obtained from experiments in which laser light is injected into one face of a finite slab of tissue and detected at the opposite face. From the results of such experiments one would like to infer optical properties of the underlying tissue which are related to its biological properties. Random walk theory has been successfully applied to the translation of such data into the physical parameters that characterize properties of the tissue. We here outline a technique based on the theory of random walks for analyzing how well time-resolved transillumination experiments may be expected to perform for detecting hidden inclusions which have a greater absorption than surrounding tissue. We use an asymptotic evaluation of exact results to determine the degree to which detection is possible.