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Mammograms of 35 patients suspected of breast cancer were taken along craniocaudal and mediolateral projections with a dual-wavelength scanning laser pulse mammograph measuring time-resolved transmittance. Among 26 tumors known from routine clinical diagnostics, 17 tumors were detected retrospectively in optical mammograms. Effective tumor optical properties derived from a homogeneous model were used to deduce physiological information. All tumors exhibited increased total hemoglobin concentration and decreased or unchanged blood oxygen saturation compared with surrounding healthy tissue. Scatter plots based on a pixelwise analysis of individual mammograms were introduced and applied to represent correlations between characteristic quantities derived from measured distributions of times of flight of photons.

We have developed a laser-pulse mammograph capable of recording optical mammograms within ∼3 min by measuring time-resolved transmittance at each of typically 1500 scan positions, 2.5 mm apart. As a first application two patients who have tumors were investigated successfully. From measured distributions of times of flight of photons corrected for edge effects we derived (1) characteristic quantities, such as photon counts in selected time windows, to generate optical mammograms; (2) effective transport scattering and absorption coefficients of breast tissue at each scan position, assuming the breast to be homogeneous; and (3) optical properties of a selected tumor by applying the theory of diffraction of photon density waves by spherical inhomogeneity. Mammograms recorded at different lateral offsets between source and detector fiber were used to estimate the depth of inhomogeneities.

We present a method for the noninvasive determination of the size, position, and optical properties (absorption and reduced scattering coefficients) of tumors in the human breast. The tumor is first detected by frequency-domain optical mammography. It is then sized, located, and optically characterized by use of diffusion theory as a model for the propagation of near-infrared light in breast tissue. Our method assumes that the tumor is a spherical inhomogeneity embedded in an otherwise homogeneous tissue. We report the results obtained on a 55-year-old patient with a papillary cancer in the right breast. We found that the tumor absorbs and scatters near-infrared light more strongly than the surrounding healthy tissue. Our method has yielded a tumor diameter of 2.1 ± 0.2 cm, which is comparable with the actual size of 1.6 cm, determined after surgery. From the tumor absorption coefficients at two wavelengths (690 and 825 nm), we calculated the total hemoglobin concentration (40 ± 10 μM) and saturation (71 ± 9%) of the tumor. These results can provide the clinical examiner with more detailed information about breast lesions detected by frequency-domain optical mammography, thereby enhancing its potential for specificity.