Time-resolved imaging of solid phantoms for optical mammography

We have recorded time-resolved transillumination images of solid phantoms with objects embedded that differ in their scattering and absorption coefficients from those of the bulk material, simulating a compressed human breast with a tumor inside. Employing time-correlated single photon counting at rates of up to 1 MHz, we recorded distributions of times of flight of photons at 1369 scan positions within 2.5 min. Several quantities, such as fractional transmittance, first moments, Fourier amplitudes, phase shifts, and frequency-dependent effective transport scattering and absorption coefficients, have been derived from experimental data to form two-dimensional images. By recording such images at a selected total number of photons detected, we have determined the contrast and effective signal-to-noise ratio in each case.