We present line scan reflectance diffuse optical tomography (LS-RDOT), a technique to generate quantitative cross-sectional images of hemoglobin concentration, tissue oxygen saturation, water content, and lipid content, for non-invasive bedside imaging of breast cancer. The LS-RDOT system is composed of a single-channel time-domain diffuse optical spectroscopy (TD-DOS) system measuring at wavelengths of 761, 802, 838, 908, 936, and 976 nm and hand-held probes with source–detector distances of 20, 30, and 40 mm. The line scans were performed by acquiring temporal point spread functions (TPSF) at 9 measurement points with a spacing of 5 mm linearly marked on the skin just above the breast lesion. The cross-sectional images were restored by an iterative image reconstruction method with an expression of the TPSF obtained from the photon diffusion equation using the Rytov approximation. A preliminary clinical measurement was conducted for a breast cancer patient with a tumor of approximately 10 mm in size. The reconstructed images captured changes in the physiological parameters of the breast cancer at the lesion location indicated by the ultrasonographic image. In addition, the results showed that LS-RDOT provides cross-sectional images of physiological parameters in a form that can be fused with structural images provided by ultrasonography
SignificanceThe water and lipid content of normal breast tissue showed mammary gland characteristics with less influence from the chest wall using six-wavelength time-domain diffuse optical spectroscopy (TD-DOS) in a reflectance geometry.AimTo determine the depth sensitivity of a six-wavelength TD-DOS system and evaluate whether the optical parameters in normal breast tissue can distinguish dense breasts from non-dense breasts.ApproachMeasurements were performed in normal breast tissue of 37 breast cancer patients. We employed a six-wavelength TD-DOS system to measure the water and lipid content in addition to the hemoglobin concentration. The breast density in mammography and optical parameters were then compared.ResultsThe depth sensitivity of the system for water and lipid content was estimated to be ∼15 mm. Our findings suggest that the influence of the chest wall on the water content is weaker than that on the total hemoglobin concentration. In data with evaluation conditions, the water content was significantly higher (p < 0.001) and the lipid content was significantly lower (p < 0.001) in dense breast tissue. The water and lipid content exhibited a high sensitivity and specificity to distinguish dense from non-dense breasts in receiver-operating-characteristic curve analysis.ConclusionsWith less influence from the chest wall, the water and lipid content of normal breast tissue measured by a reflectance six-wavelength TD-DOS system, together with ultrasonography, can be applied to distinguish dense from non-dense breasts.
We report a time-domain reflectance diffuse optical tomography (TD-RDOT) system for providing three-dimensional images of hemoglobin concentration, tissue oxygen saturation, water and lipid contents of breast cancer from reflectance measurements. A scan area of 5 × 5 grid points with a 10-mm spacing is marked on the breast surface so that the tumor is just below the center of the area. The breast scan is performed by measuring the temporal profiles of six wavelengths at each grid point using a time-domain diffuse optical spectroscopy (TD-DOS) system and a hand-held probe. The TDDOS system that we developed is capable of measuring water and lipid contents and hemoglobin concentration. The hand-held probe is designed to measure the breast in reflectance mode with a source-to-detector separation of 20 mm. The three-dimensional distributions of the tissue parameters are restored using an iterative image reconstruction method. As a preliminary clinical demonstration, a breast cancer patient with a tumor size of approximately 20 mm was examined with the TD-RDOT. The reconstructed images show that the breast cancer had high hemoglobin concentration and water content, and low tissue oxygen saturation and lipid content. The results indicate that the TD-RDOT system has the potential to provide diagnostically relevant information on the tissue characteristics of the tumor at the bedside.
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