We used near-infrared spectroscopy to separate tissue scattering changes from changes in cerebral oxyhemoglobin and deoxyhemoglobin and the redox state of cytochrome--oxidase. A separate term of the transport scattering coefficient was included in a modified Lambert–Beer equation. It is shown by diffusion equation analysis that there is a simple relationship between the differential path-length factor and its scattering equivalent . The method was applied to cortical spreading depression (CSD) data recorded through the skulls of rats. Biphasic changes in of were observed during CSD's that spread with a velocity of . The method proposed has the promise to permit monitoring of scattering changes noninvasively in humans during cortical activation or pathophysiological conditions.
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