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Proceedings Paper

Quantifying the cortical contribution to the NIRS signal using simultaneous NIRS-BOLD measurements
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Paper Abstract

Near-Infrared Spectroscopy (NIRS) measures the functional hemodynamic response occuring at the surface of the cortex. Large pial veins are located above the surface of the cerebral cortex. Following activation, these veins exhibit oxygenation changes but their volume likely stays constant. The back-reflection geometry of the NIRS measurement renders the signal very sensitive to these superficial pial veins. As such, the measured NIRS signal contains contributions from both the cortical region as well as the pial vasculature. In this work, the cortical contribution to the NIRS signal was investigated using (1) Monte Carlo simulations over a realistic geometry constructed from anatomical and vascular MRI and (2) multimodal NIRS-BOLD recordings during motor stimulation. A good agreement was found between the simulations and the modeling analysis of in vivo measurements. Our results suggest that the cortical contribution to the deoxyhemoglobin signal change (ΔHbR) is equal to 16-22% of the cortical contribution to the total hemoglobin signal change (ΔHbT). Similarly, the cortical contribution of the oxyhemoglobin signal change (ΔHbO) is equal to 73-79% of the cortical contribution to the ΔHbT signal. These results suggest that ΔHbT is far less sensitive to pial vein contamination and therefore, it is likely that the ΔHbT signal provides better spatial specificity and should be used instead of ΔHbO or ΔHbR to map cerebral activity with NIRS. While different stimuli will result in different pial vein contributions, our finger tapping results do reveal the importance of considering the pial contribution.

Paper Details

Date Published: 29 February 2012
PDF: 12 pages
Proc. SPIE 8216, Multimodal Biomedical Imaging VII, 82160F (29 February 2012); doi: 10.1117/12.909629
Show Author Affiliations
Louis Gagnon, Harvard Medical School (United States)
Harvard-MIT Division of Health Sciences and Technology (United States)
Meryem A. Yücel, Harvard Medical School (United States)
Mathieu Dehaes, Children's Hospital Boston (United States)
Harvard Medical School (United States)
Robert J. Cooper, Harvard Medical School (United States)
Katherine L. Perdue, Dartmouth College (United States)
Juliette Selb, Harvard Medical School (United States)
David A. Boas, Harvard Medical School (United States)
Harvard-MIT Division of Health Sciences and Technology (United States)


Published in SPIE Proceedings Vol. 8216:
Multimodal Biomedical Imaging VII
Fred S. Azar; Xavier Intes, Editor(s)

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