Attenuation of energy in time-gated transillumination imaging: numerical results

Numerical simulations based on a semianalytic Monte Carlo procedure have been developed to investigate the feasibility of a time-gated transillumination imaging system that could be useful for breast cancer screening. Numerical results showed that attenuation of earlier received photons strongly increases when the gating time decreases and strongly depends on single-scattering properties of the medium. For gating times shorter than ~ 5 ps, attenuation of scattered received energy approaches the exponential attenuation expected for unscattered photons. For typical optical properties of a healthy breast the use of gating times shorter than 100 ps seems to be questionable because of the low level of received energy. The image resolution expected with gating times longer than lOOps is of the order of 10mm. A comparison with predictions or the diffusion equation showed the inadequacy of this theory to describe the dependence of earlier photons on the single-scattering properties of the medium. However, thepredictions of the diffusion equation are within the range of values obtained from numerical simulations for the different scattering properties investigated.