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Abstract:
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In my optical spectroscopy study , multi -channel , thin optical probes with short source -detector separation have been implemented , calibrated , and used along with a multi -channel spectrometer as a quantitative technique to observe changes in vascular hemoglobin concentration and hemoglobin oxygen saturation as well as light scattering of tissues . Each of the four needle probes used in my study consists of two bifurcated fibers ; one fiber is connected to a halogen light source and the other fiber to a CCD -array spectrometer having a spectral window from 450 nm to 900 nm . Each fiber is 100 micron in diameter . As we utilized the four probes individually and simultaneously , a source multiplexer and a multi -channel spectrometer were used during the measurement . For quantification of tissue physiological parameters , each probe needed to be calibrated to remove the instrumentation effects . The laboratory experiments using liquid tissue phantoms were conducted to calibrate the probes and to validate the algorithm that was developed to quantify oxygenated [HbO] and deoxygenated [Hb] hemoglobin concentrations and scattering coefficients . These calibrated probes were then applied for the pain study in rats . Two probes were placed on the spinal cord and two on the primary somatosensory (S1 ) region of the rat brain , each on the ipsilateral and contralateral sides of the rat . While the paw of the rat was stimulated using electrical stimulations , hemodynamic responses were acquired at the four locations on the rat . The results showed a significant increase in [HbO] and a decrease in [Hb] at the ipsilateral side of the spinal cord and contrlateral side of the S1 region of the brain , caused by the electrical stimulation at the paw . My study demonstrates that multi -channel reflectance spectroscopy is a useful tool to study pain mechanism at different central nervous sites using animal models . |