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  Elimination of visually evoked BOLD responses during carbogen inhalation: Implications for calibrated MRI

Gauthier, C., Madjar, C., Tancredi, F. B., Stefanovic, B., & Hoge, R. D. (2011). Elimination of visually evoked BOLD responses during carbogen inhalation: Implications for calibrated MRI. NeuroImage, 54(2), 1001-1011. doi:10.1016/j.neuroimage.2010.09.059.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-77ED-2 Version Permalink: http://hdl.handle.net/21.11116/0000-0002-B350-9
Genre: Journal Article

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 Creators:
Gauthier, Claudine1, 2, Author              
Madjar, Cécile2, Author
Tancredi, Felipe B.1, 2, Author
Stefanovic, Bojana3, Author
Hoge, Richard D.1, 2, Author
Affiliations:
1Department of Physiology, Institute of Biomedical Engineering, University of Montréal, QC, Canada, ou_persistent22              
2Centre de recherche de l'Institut universitaire de gériatrie de Montréal, QC, Canada, ou_persistent22              
3Department of Medical Biophysics, University of Toronto, ON, Canada, ou_persistent22              

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Free keywords: Calibrated MRI; Carbogen; Hypercapnia; Hyperoxia; Oxygen metabolism; Venous saturation
 Abstract: Breathing a mixture of 10% CO2 with 90% O2 (referred to here as carbogen-10) increases blood flow due to the vasodilatory effect of CO2, and raises blood O2 saturation due to the enriched oxygen level. These effects both tend to reduce the level of deoxygenated hemoglobin in brain tissues, thereby reducing the potential for further increases in BOLD contrast. In the present study, blocks of intense visual stimulation (60 s) were presented amid longer blocks (180 s) during which subjects breathed various fractional concentrations (0–100%) of carbogen-10 diluted with medical air. When breathing undiluted carbogen-10, the BOLD response to visual stimulation was reduced below the level of noise against the background of the carbogen-10 response. At these concentrations, the total (visual+carbogen) BOLD response amplitude (7.5±1.0%, n=6) converged toward that seen with carbogen alone (7.5 ± 1.0%, n = 6). In spite of the almost complete elimination of the visual BOLD response, pseudo-continuous arterial spin-labeling on a separate cohort indicated a largely preserved perfusion response (89±34%, n=5) to the visual stimulus during inhalation of carbogen-10. The previously discussed observations suggest that venous saturation can be driven to very high levels during carbogen inhalation, a finding which has significant implications for calibrated MRI techniques. The latter methods involve estimation of the relative change in venous O2 saturation by expressing activation-induced BOLD signal increases as a fraction of the maximal BOLD signal M that would be observed as venous saturation approaches 100%. While the value of M has generally been extrapolated from much smaller BOLD responses induced using hypercapnia or hyperoxia, our results suggest that these effects could be combined through carbogen inhalation to obtain estimates of M based on larger BOLD increases. Using a hybrid BOLD calibration model taking into account changes in both blood flow and arterial oxygenation, we estimated that inhalation of carbogen-10 led to an average venous saturation of 91%, allowing us to compute an estimated M value of 9.5%.

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Language(s): eng - English
 Dates: 2010-09-142010-05-272010-09-212010-09-292011-01-15
 Publication Status: Published in print
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 Table of Contents: -
 Rev. Method: Peer
 Identifiers: DOI: 10.1016/j.neuroimage.2010.09.059
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Title: NeuroImage
Source Genre: Journal
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Publ. Info: Orlando, FL : Academic Press
Pages: - Volume / Issue: 54 (2) Sequence Number: - Start / End Page: 1001 - 1011 Identifier: ISSN: 1053-8119
CoNE: https://pure.mpg.de/cone/journals/resource/954922650166