Non-invasive detection and quantification of brain microvascular deficits by near-infrared spectroscopy in a rat model of vascular cognitive impairment

Bertan Hallacoglu*, Angelo M. Sassaroli, Irwin H. Rosenberg, Aron Troen, Sergio Fantini

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

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 (StO 2) 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.

Original languageAmerican English
Title of host publicationOptical Tomography and Spectroscopy of Tissue IX
DOIs
StatePublished - 2011
EventOptical Tomography and Spectroscopy of Tissue IX - San Francisco, CA, United States
Duration: 23 Jan 201126 Jan 2011

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume7896
ISSN (Print)1605-7422

Conference

ConferenceOptical Tomography and Spectroscopy of Tissue IX
Country/TerritoryUnited States
CitySan Francisco, CA
Period23/01/1126/01/11

Keywords

  • Near-infrared spectroscopy
  • cerebral hemodynamics
  • hemoglobin saturation
  • photon migration
  • vascular cognitive impairment

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