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Proceedings Paper

Non-invasive detection and quantification of brain microvascular deficits by near-infrared spectroscopy in a rat model of Vascular Cognitive Impairment
Author(s): Bertan Hallacoglu; Angelo M. Sassaroli; Irwin H. Rosenberg; Aron Troen; Sergio Fantini
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Paper Abstract

Structural abnormalities in brain microvasculature are commonly associated with Alzheimer's Disease and other dementias. However, the extent to which structural microvascular abnormalities cause functional impairments in brain circulation and thereby to cognitive impairment is unclear. Non-invasive, near-infrared spectroscopy (NIRS) methods can be used to determine the absolute hemoglobin concentration and saturation in brain tissue, from which additional parameters such as cerebral blood volume (a theoretical correlate of brain microvascular density) can be derived. Validating such NIRS parameters in animal models, and understanding their relationship to cognitive function is an important step in the ultimate application of these methods to humans. To this end we applied a non-invasive multidistance NIRS method to determine the absolute concentration and saturation of cerebral hemoglobin in rat, by separately measuring absorption and reduced scattering coefficients without relying on pre- or post-correction factors. We applied this method to study brain circulation in folate deficient rats, which express brain microvascular pathology1 and which we have shown to develop cognitive impairment.2 We found absolute brain hemoglobin concentration ([HbT]) and oxygen saturation (StO2) to be significantly lower in folate deficient rats (n=6) with respect to control rats (n=5) (for [HbT]: 73±10 μM vs. 95±14 μM; for StO2: 55%±7% vs. 66% ±4%), implicating microvascular pathology and diminished oxygen delivery as a mechanism of cognitive impairment. More generally, our study highlights how noninvasive, absolute NIRS measurements can provide unique insight into the pathophysiology of Vascular Cognitive Impairment. Applying this method to this and other rat models of cognitive impairment will help to validate physiologically meaningful NIRS parameters for the ultimate goal of studying cerebral microvascular disease and cognitive decline in humans.

Paper Details

Date Published: 1 March 2011
PDF: 7 pages
Proc. SPIE 7896, Optical Tomography and Spectroscopy of Tissue IX, 789608 (1 March 2011); doi: 10.1117/12.875076
Show Author Affiliations
Bertan Hallacoglu, Tufts Univ. (United States)
Angelo M. Sassaroli, Tufts Univ. (United States)
Irwin H. Rosenberg, Tufts Univ. (United States)
Aron Troen, Tufts Univ. (United States)
The Hebrew Univ. of Jerusalem (Israel)
Sergio Fantini, Tufts Univ. (United States)

Published in SPIE Proceedings Vol. 7896:
Optical Tomography and Spectroscopy of Tissue IX
Bruce Jason Tromberg; Arjun G. Yodh; Mamoru Tamura; Eva Marie Sevick-Muraca; Robert R. Alfano, Editor(s)

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