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
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.
Time-domain (TD) near-infrared spectroscopy (NIRS) is an effective method of quantifying optical and biological properties, such as the mean optical path length, absorption coefficient, reduced scattering coefficient, and oxyhemoglobin and deoxy-hemoglobin concentrations of biological tissues. In addition to these parameters, water and lipid contents are important biological parameters expected to be useful information in clinical application. For our previous TD-NIRS systems, we used three wavelengths (760, 800, and 830 nm) that are sensitive to oxy- and deoxy-hemoglobin. To quantitatively measure water and lipid contents of biological tissues, we developed a new TD-NIRS system with three additional wavelengths (908, 936, and 976 nm) that are sensitive to water and lipids. The new six-wavelength TDNIRS system comprises six-wavelength pulsed light sources, two types of photomultiplier tubes (GaAs and InGaAs PMTs), a time-correlated single-photon counting unit, and optical fiber bundles. In this pilot study, we present the measurement results of oxy- and deoxy-hemoglobin concentrations, tissue oxygen saturation, and water and lipid contents at the calf, forearm, and abdomen of five healthy adult volunteers in a resting state using the six-wavelength TD-NIRS system. We thus confirmed that the fat thickness measured by ultrasonography and the water content measured by the six-wavelength TD-NIRS system were negatively correlated, whereas the fat thickness and lipid content were positively correlated. We expect that the six-wavelength TD-NIRS system will be used in clinical studies as a point-of-care testing device for the bedside monitoring of human subjects.
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