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Journal of Biomedical Optics

Imaging cortical absorption, scattering, and hemodynamic response during ischemic stroke using spatially modulated near-infrared illumination
Author(s): David Abookasis; Christopher C. Lay; Marlon Stephen Mathews; Mark E. Linskey; Ron D. Frostig; Bruce Jason Tromberg
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Paper Abstract

We describe a technique that uses spatially modulated near-infrared (NIR) illumination to detect and map changes in both optical properties (absorption and reduced scattering parameters) and tissue composition (oxy- and deoxyhemoglobin, total hemoglobin, and oxygen saturation) during acute ischemic injury in the rat barrel cortex. Cerebral ischemia is induced using an open vascular occlusion technique of the middle cerebral artery (MCA). Diffuse reflected NIR light (680 to 980 nm) from the left parietal somatosensory cortex is detected by a CCD camera before and after MCA occlusion. Monte Carlo simulations are used to analyze the spatial frequency dependence of the reflected light to predict spatiotemporal changes in the distribution of tissue absorption and scattering properties in the brain. Experimental results from seven rats show a 17±4.7% increase in tissue concentration of deoxyhemoglobin and a 45±3.1, 23±5.4, and 21±2.2% decrease in oxyhemoglobin, total hemoglobin concentration and cerebral tissue oxygen saturation levels, respectively, 45 min following induction of cerebral ischemia. An ischemic index (Iisch=ctHHb/ctO2Hb) reveals an average of more then twofold contrast after MCAo. The wavelength-dependence of the reduced scattering (i.e., scatter power) decreased by 35±10.3% after MCA occlusion. Compared to conventional CCD-based intrinsic signal optical imaging (ISOI), the use of structured illumination and model-based analysis allows for generation of separate maps of light absorption and scattering properties as well as tissue hemoglobin concentration. This potentially provides a powerful approach for quantitative monitoring and imaging of neurophysiology and metabolism with high spatiotemporal resolution.

Paper Details

Date Published: 1 March 2009
PDF: 9 pages
J. Biomed. Opt. 14(2) 024033 doi: 10.1117/1.3116709
Published in: Journal of Biomedical Optics Volume 14, Issue 2
Show Author Affiliations
David Abookasis, Univ. of California, Irvine (United States)
Christopher C. Lay, Univ. of California, Irvine (United States)
Marlon Stephen Mathews, Univ. of California, Irvine (United States)
Mark E. Linskey, Univ. of California, Irvine (United States)
Ron D. Frostig, Univ. of California, Irvine (United States)
Bruce Jason Tromberg, Univ. of California, Irvine (United States)


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