Analysis of time-domain optical mammograms recorded from more than 150 patients

We used a scanning laser pulse mammograph to record craniocaudal and mediolateral projection optical mammograms of 154 patients suspected to have breast cancer. Optical mammograms were analyzed by comparing them with x-ray and MR mammograms, including results of histopathology. Out of 102 histologically confirmed carcinomas, 92 carcinomas were visible in at least one of the two projection mammograms. On average optical mammograms based on photon counts in a late time window exhibited the carcinomas with highest contrast compared to mammograms displaying absorption coefficients or hemoglobin concentration. Optical properties of carcinomas visible in optical mammograms were determined employing the model of diffraction of photon density waves by a spherical inhomogeneity, located in an otherwise homogeneous tissue slab. On average, tumor absorption coefficients exceeded those of surrounding healthy breast tissue by a factor of about 2.5 at the shortest wavelength used (670 nm), whereas tumor reduced scattering coefficients were larger by about 20% at this wavelength. Total hemoglobin concentration was observed to be systematically larger in tumors compared to healthy breast tissue. In contrast, blood oxygen saturation was found to be a poor discriminator for tumors and healthy breast tissue.