Time-domain laser mammography: separation of scattering and absorption contributions

ABSTRACT A technique for properly separating the scattering and absorption contributions in laser mammography is proposed. Thetechnique is based on an empirical model obtained from a series of experiments performed on homogeneous scattering slabs containing a single inclusion. The scattering and absorption contributions are obtained by performing a Fit of an Inhomogeneous Diffusion Model (FIDM). The performance of this new technique is compared to that involving a curve fit ofthe solution of the diffusion model for a homogeneous slab. The FIDM technique allows a very good discrimination betweenscattering and absorption inclusions, better than that obtained with a curve fit of the homogeneous diffusion model. Themathematical expressions of the empirical model are extremely simple and allow for a fast calculation (about 1 second forcomputing two 44 1 pixel images compared to about 6 minutes with the previous technique). A perturbation analysis of thediffusion model will provide theoretical support to the FIDM technique and should allow its refinement. Although it has notbeen demonstrated that the separation between absorption and scattering is totally correct when applied to real breastscanning, the method associates some structures to absorption and some other to scattering, which could result in a betterspecificity of laser mammography.Keywords: Turbid medium, photon migration, time-resolved, mammography, breast cancer, perturbation analysis.