ATTENUATION OF ENERGY IN TIME-GATED TRANSILLUMINATION IMAGING - NUMERICAL RESULTS

Numerical simulations based on a semianalytic Monte Carlo procedure ha ve been developed to investigate the feasibility of a time-gated trans illumination imaging system that could be useful for breast cancer scr eening. Numerical results showed that attenuation of ealier received p hotons strongly increases when the gating time decreases and strongly depends on single-scattering properties of the medium. For gating time s shorter than approximately 5 ps, attenuation of scattered received e nergy 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 g ating times longer than 100 ps is of the order of 10 mm. A comparison with predictions or the diffusion equation showed the inadequacy of th is theory to describe the dependence of earlier photons on the single- scattering properties of the medium. However, the predictions of the d iffusion equation are within the range of values obtained from numeric al simulations for the different scattering properties investigated.