An algorithm based on a discrete model for photon migration is proposed for recovering the absorption coefficient in a semi-infinite slab. A pulsed light source is modeled and only reflected signals are used in the reconstruction. The diffusion coefficient and speed of light are assumed constant and known. The algorithm is based on the result that the earliest reflected signals obtained from a particular voxel depend either in a linear or in a quadratical fashion on the square of the absorption coefficient in that voxel. By solving the discrete model in the forward direction in a region where the absorption coefficient has been calculated already, the absorption coefficients in the voxels on the boundary of the region are calculated using interpolation.
Results show that simple absorptive regions can be accurately recovered.