Accuracy of a perturbation model to predict the effect of scattering and absorbing inhomogeneities on photon migration

The accuracy of the perturbation model to predict the effect of scattering and absorbing inhomogeneities on photon migration has been investigated by comparisons with experimental and numerical results. Comparisons for scatte ring inhomogeneities showed that the model gives satisfactory results both for the intensity and for the temporal profile of the perturbation over a l arge range of values for the scattering properties of the defect. As for ab sorbing inhomogeneities, the model provides an excellent description for th e temporal profile, but the results for the intensity are accurate only whe n the perturbation is small. For absorbing inhomogeneities an empirical mod el that has a significantly more extended application range has been propos ed. The model is based on an expression for the time-resolved mean path len gth that detected photons have followed inside the inhomogeneity. The appli cation range of the proposed model covers the values expected for the optic al properties and for the volumes of inhomogeneities of practical interest for optical mammography. (C) 2001 Optical Society of America.