We used near-infrared spectroscopy to separate tissue scattering changes from changes in cerebral oxyhemoglobin and deoxyhemoglobin and the redox state of cytochrome- c -oxidase. A separate term of the transport scattering coefficient (µ<sub>s</sub><sup>′</sup>) 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 (D<sub>a</sub>) and its scattering equivalent (D<sub>s</sub>) . The method was applied to cortical spreading depression (CSD) data recorded through the skulls of rats. Biphasic changes in µ<sub>s</sub><sup>′</sup>of ±0.1mm<sup>-1</sup>were observed during CSD’s that spread with a velocity of ~5mm/min . The method proposed has the promise to permit monitoring of scattering changes noninvasively in humans during cortical activation or pathophysiological conditions.
© 1998 Optical Society of America
(170.1470) Medical optics and biotechnology : Blood or tissue constituent monitoring
(170.3660) Medical optics and biotechnology : Light propagation in tissues
(170.5280) Medical optics and biotechnology : Photon migration
(170.6930) Medical optics and biotechnology : Tissue
Matthias Kohl, Ute Lindauer, Ulrich Dirnagl, and Arno Villringer, "Separation of changes in light scattering and chromophore concentrations during cortical spreading depression in rats," Opt. Lett. 23, 555-557 (1998)