Abstract: We study the optical detection of absorptive tumors in turbid tissues, using a random-walk model to describe the migration of photons in the tissue. We consider time-resolved transillumination measurements in slab-like tissues, and calculate the tranmsmitted intensity with and without the inclusion. The ratio of these quantities, defined as the measure of the detectability, is studied as a function of the inclusion size and absorption coefficient. The detectability is found to depend only on the difference between the absorptivities of the abnormality and the surrounding tissue. The nonmonotonic behavior in time of this ratio corresponds to the three different types of photon trajectories in the tissue, and its extremum points provide information which can be used to determine the optimal time window for best detection. !20
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