Use Of Near Infrared And Visible Spectroscopies To Determine Optical Properties Of Rat Nervous System

Changes to the anatomical or physiological structure of the neuronal circuitry are known to produce a change in the optical properties of the tissue under investigation. The goal of this thesis is to determine changes in the light scattering and hemoglobin oxygen saturation in three cases: (i) a normal spinal cord, (ii) demyelinated sciatic nerve, and (iii) spinal cord under neuronal activity induced by peripheral electrical stimulation. We hypothesize that (i) nerve demyelination or degeneration would result in a decrease in light scattering and hemoglobin oxygen saturation and (ii) peripheral electrical stimulation would show an increase in light scattering and hemoglobin oxygen saturation. The experiments were done using a one source, one detector fiber optic needle probe with a source-detector separation of 100 microns. Optical reflectance data was obtained using the probe connected to a CCD array spectrometer grated in the wavelength range of 350 to 1100 nm. We used prior developed algorithms for detecting reduced scattering coefficient and hemoglobin oxygen saturation. Based on the spectral data obtained, we statistically proved all our hypotheses.