A perturbation approach for optical characterization of absorptive inclusions in diffusing media by time-resolved contrast measurements

We have performed a detailed analysis for the problem of photon migration through a scattering slab containing a single absorptive inclusion whose absorption coefficient is characterized by a spatially varying Gaussian distribution law. The analysis has been performed within the framework of the first-order perturbation approach to the diffusion theory for a slab geometry and a coaxial measurements arrangement. An analytical expression has been derived that account for the change in the time-resolved transmittance in presence of the absorptive Gaussian inclusion. We present experimental results of time-resolved measurements that have been performed on absorptive phantoms with the aim to investigate and to validate the ability of this model to predict the optical properties of absorptive inhomogeneities hidden inside a scattering medium