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.
We developed a time-resolved reflectance diffuse optical tomography (RDOT) system to measure tumor responses to chemotherapy in breast cancer patients at the bedside. This system irradiates the breast with a three-wavelength pulsed laser (760, 800, and 830 nm) through a source fiber specified by an optical switch. The light collected by detector fibers is guided to a detector unit consisting of variable attenuators and photomultiplier tubes. Thirteen irradiation and 12 detection points were set to a measurement area of 50 × 50 mm for a hand-held probe. The data acquisition time required to obtain the temporal profiles within the measurement area is about 2 minutes. The RDOT system generates topographic and tomographic images of tissue properties such as hemoglobin concentration and tissue oxygen saturation using two imaging methods. Topographic images are obtained from the optical properties determined for each source-detector pair using a curve-fitting method based on the photon diffusion theory, while tomographic images are reconstructed using an iterative image reconstruction method. In an experiment using a tissue-like solid phantom, a tumor-like cylindrical target (15 mm diameter, 15 mm high) embedded in a breast tissue-like background medium was successfully reconstructed. Preliminary clinical measurements indicated that the tumor in a breast cancer patient was detected as a region of high hemoglobin concentration. In addition, the total hemoglobin concentration decreased during chemotherapy. These results demonstrate the potential of RDOT for evaluating the effectiveness of chemotherapy in patients with breast cancer.
Near-infrared spectroscopy (NIRS) has been used for noninvasive assessment of oxygenation in living tissue. For muscle measurements by NIRS, the measurement sensitivity to muscle (SM) is strongly influenced by fat thickness (FT). In this study, we investigated the influence of FT and developed a correction curve for SM with an optode distance (3 cm) sufficiently large to probe the muscle. First, we measured the hemoglobin concentration in the forearm (n=36) and thigh (n=6) during arterial occlusion using a time-resolved spectroscopy (TRS) system, and then FT was measured by ultrasound. The correction curve was derived from the ratio of partial mean optical path length of the muscle layer 〈LM〉 to observed mean optical path length 〈L〉. There was good correlation between FT and 〈L〉 at rest, and 〈L〉 could be used to estimate FT. The estimated FT was used to validate the correction curve by measuring the forearm blood flow (FBF) by strain-gauge plethysmography (SGP_FBF) and TRS (TRS_FBF) simultaneously during a reactive hyperemia test with 16 volunteers. The corrected TRS_FBF results were similar to the SGP_FBF results. This is a simple method for sensitivity correction that does not require use of ultrasound.
Using near-infrared time-resolved spectroscopy (TRS), we measured the human head in transmittance mode to obtain the
optical properties, tissue oxygenation, and hemodynamics of deep brain tissues in 50 healthy adult volunteers. The right
ear canal was irradiated with 3-wavelengths of pulsed light (760, 795, and 835nm), and the photons passing through the
human head were collected at the left ear canal. Optical signals with sufficient intensity could be obtained from 46 of the
50 volunteers. By analyzing the temporal profiles based on the photon diffusion theory, we successfully obtained
absorption coefficients for each wavelength. The levels of oxygenated hemoglobin (HbO2), deoxygenated hemoglobin
(Hb), total hemoglobin (tHb), and tissue oxygen saturation (SO2) were then determined by referring to the hemoglobin
spectroscopic data. Compared with the SO2 values for the forehead measurements in reflectance mode, the SO2 values of the transmittance measurements of the human head were approximately 10% lower, and tHb values of the transmittance measurements were always lower than those of the forehead reflectance measurements. Moreover, the level of
hemoglobin and the SO2 were strongly correlated between the human head measurements in transmittance mode and the forehead measurements in the reflectance mode, respectively. These results demonstrated a potential application of this TRS system in examining deep brain tissues of humans.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.