Applied optics
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An easy and accurate assessment of the renal function is a critical requirement for detecting the initial functional decline of the kidney induced by acute or chronic renal disease. A method for measuring the glomerular filtration rate is developed with the accuracy of clearance techniques and the convenience of plasma creatinine. ⋯ The agent has a large dose-safety coefficient and the same space distribution and clearance characteristics as iothalamate. This new approach is a convenient and accurate way to perform real-time measurements of the glomerular filtration rate to detect early kidney disease before the renal function becomes severely and irreversibly compromised.
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A novel magnetic-resonance-coupled broadband near-infrared (NIR) tomography system for small animal brain studies is described. Several features of the image formation approach are new in NIR tomography and represent major advances in the path to recovering high-resolution hemoglobin and oxygen saturation images of tissue. The NIR data were broadband and continuous wave and were used along with a second-derivative-based estimation of the path length from water absorption. ⋯ The latter experiment used variation in inspired oxygen (FiO2) to vary the observed hemoglobin and oxygen saturation images. Quantitative agreement was observed between the changes in deoxyhemoglobin values derived from NIR and the changes predicted with blood-oxygen-level-dependent (BOLD) MRI. This system represents the initial stage in what will likely be a larger role for NIR tomography, coupled to MRI, and illustrates that the technological challenges of using continuous-wave broadband data and inclusion of a priori structural information can be met with careful phantom studies.
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Comparative Study
Continuous, noninvasive monitoring of total hemoglobin concentration by an optoacoustic technique.
Measurement of total hemoglobin concentration [Hgb] is a blood test that is widely used to evaluate outpatients, hospital inpatients, and surgical patients, especially those undergoing surgery associated with extensive blood loss, rapid fluid administration, and transfusion of packed red blood cells. Current techniques for measurement of [Hgb] are invasive (requiring blood sampling) and cannot provide real-time, continuous monitoring. We propose to use an optoacoustic technique for noninvasive and continuous monitoring of [Hgb]. ⋯ The system includes a nanosecond laser operating in the near-infrared spectral range and a sensitive optoacoustic probe designed to irradiate the radial artery through the skin and detect optoacoustic signals induced in blood. Results of our studies demonstrated that (1) the slope of optoacoustic waves induced in blood in the transmission mode is linearly dependent on [Hgb] in the range from 6.2 to 12.4 g/dl, (2) optoacoustic signals can be detected despite optical attenuation in turbid tissue phantoms with a thickness of 1 cm, and (3) the optoacoustic system detects signals induced in blood circulating in the radial artery. These data suggest that the optoacoustic system can be used for accurate, noninvasive, real-time, and continuous monitoring of [Hgb].
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Based on the negabinary number representation, parallel one-step arithmetic operations (that is, addition and subtraction), logical operations, and matrix-vector multiplication on data have been optically implemented, by use of a two-dimensional spatial-encoding technique. For addition and subtraction, one of the operands in decimal form is converted into the unsigned negabinary form, whereas the other decimal number is represented in the signed negabinary form. The result of operation is obtained in the mixed negabinary form and is converted back into decimal. ⋯ Both of the operands for logical operation are converted to their signed negabinary forms. All operations are implemented by use of a unique optical architecture. The use of a single liquid-crystal-display panel to spatially encode the input data, operational kernels, and decoding masks have simplified the architecture as well as reduced the cost and complexity.
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The theory of special relativity is used to analyze some of the physical phenomena associated with space-based coherent Doppler lidars aimed at Earth and the atmosphere. Two important cases of diffuse scattering and retroreflection by lidar targets are treated. For the case of diffuse scattering, we show that for a coaligned transmitter and receiver on the moving satellite, there is no angle between transmitted and returned radiation. ⋯ The results are then applied to a proposed space-based pulsed coherent Doppler lidar at NASA's Marshall Space Flight Center for wind and aerosol backscatter measurements. The lidar uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and the received frequencies to determine the atmospheric wind velocities. We show that the special relativity effects are small for the proposed system.