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The impact of inspired oxygen levels on calibrated fMRI measurements of M, OEF and resting CMRO(2) using combined hypercapnia and hyperoxia

Recent calibrated fMRI techniques using combined hypercapnia and hyperoxia allow the mapping of resting cerebral metabolic rate of oxygen (CMRO(2)) in absolute units, oxygen extraction fraction (OEF) and calibration parameter M (maximum BOLD). The adoption of such technique necessitates knowledge ab...

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Autores principales: Lajoie, Isabelle, Tancredi, Felipe B., Hoge, Richard D.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5376305/
https://www.ncbi.nlm.nih.gov/pubmed/28362834
http://dx.doi.org/10.1371/journal.pone.0174932
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author Lajoie, Isabelle
Tancredi, Felipe B.
Hoge, Richard D.
author_facet Lajoie, Isabelle
Tancredi, Felipe B.
Hoge, Richard D.
author_sort Lajoie, Isabelle
collection PubMed
description Recent calibrated fMRI techniques using combined hypercapnia and hyperoxia allow the mapping of resting cerebral metabolic rate of oxygen (CMRO(2)) in absolute units, oxygen extraction fraction (OEF) and calibration parameter M (maximum BOLD). The adoption of such technique necessitates knowledge about the precision and accuracy of the model-derived parameters. One of the factors that may impact the precision and accuracy is the level of oxygen provided during periods of hyperoxia (HO). A high level of oxygen may bring the BOLD responses closer to the maximum M value, and hence reduce the error associated with the M interpolation. However, an increased concentration of paramagnetic oxygen in the inhaled air may result in a larger susceptibility area around the frontal sinuses and nasal cavity. Additionally, a higher O(2) level may generate a larger arterial blood T(1) shortening, which require a bigger cerebral blood flow (CBF) T(1) correction. To evaluate the impact of inspired oxygen levels on M, OEF and CMRO(2) estimates, a cohort of six healthy adults underwent two different protocols: one where 60% of O(2) was administered during HO (low HO or LHO) and one where 100% O(2) was administered (high HO or HHO). The QUantitative O2 (QUO2) MRI approach was employed, where CBF and R2* are simultaneously acquired during periods of hypercapnia (HC) and hyperoxia, using a clinical 3 T scanner. Scan sessions were repeated to assess repeatability of results at the different O(2) levels. Our T(1) values during periods of hyperoxia were estimated based on an empirical ex-vivo relationship between T(1) and the arterial partial pressure of O(2). As expected, our T(1) estimates revealed a larger T(1) shortening in arterial blood when administering 100% O(2) relative to 60% O(2) (T(1LHO) = 1.56±0.01 sec vs. T(1HHO) = 1.47±0.01 sec, P < 4*10(−13)). In regard to the susceptibility artifacts, the patterns and number of affected voxels were comparable irrespective of the O(2) concentration. Finally, the model-derived estimates were consistent regardless of the HO levels, indicating that the different effects are adequately accounted for within the model.
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spelling pubmed-53763052017-04-07 The impact of inspired oxygen levels on calibrated fMRI measurements of M, OEF and resting CMRO(2) using combined hypercapnia and hyperoxia Lajoie, Isabelle Tancredi, Felipe B. Hoge, Richard D. PLoS One Research Article Recent calibrated fMRI techniques using combined hypercapnia and hyperoxia allow the mapping of resting cerebral metabolic rate of oxygen (CMRO(2)) in absolute units, oxygen extraction fraction (OEF) and calibration parameter M (maximum BOLD). The adoption of such technique necessitates knowledge about the precision and accuracy of the model-derived parameters. One of the factors that may impact the precision and accuracy is the level of oxygen provided during periods of hyperoxia (HO). A high level of oxygen may bring the BOLD responses closer to the maximum M value, and hence reduce the error associated with the M interpolation. However, an increased concentration of paramagnetic oxygen in the inhaled air may result in a larger susceptibility area around the frontal sinuses and nasal cavity. Additionally, a higher O(2) level may generate a larger arterial blood T(1) shortening, which require a bigger cerebral blood flow (CBF) T(1) correction. To evaluate the impact of inspired oxygen levels on M, OEF and CMRO(2) estimates, a cohort of six healthy adults underwent two different protocols: one where 60% of O(2) was administered during HO (low HO or LHO) and one where 100% O(2) was administered (high HO or HHO). The QUantitative O2 (QUO2) MRI approach was employed, where CBF and R2* are simultaneously acquired during periods of hypercapnia (HC) and hyperoxia, using a clinical 3 T scanner. Scan sessions were repeated to assess repeatability of results at the different O(2) levels. Our T(1) values during periods of hyperoxia were estimated based on an empirical ex-vivo relationship between T(1) and the arterial partial pressure of O(2). As expected, our T(1) estimates revealed a larger T(1) shortening in arterial blood when administering 100% O(2) relative to 60% O(2) (T(1LHO) = 1.56±0.01 sec vs. T(1HHO) = 1.47±0.01 sec, P < 4*10(−13)). In regard to the susceptibility artifacts, the patterns and number of affected voxels were comparable irrespective of the O(2) concentration. Finally, the model-derived estimates were consistent regardless of the HO levels, indicating that the different effects are adequately accounted for within the model. Public Library of Science 2017-03-31 /pmc/articles/PMC5376305/ /pubmed/28362834 http://dx.doi.org/10.1371/journal.pone.0174932 Text en © 2017 Lajoie et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Lajoie, Isabelle
Tancredi, Felipe B.
Hoge, Richard D.
The impact of inspired oxygen levels on calibrated fMRI measurements of M, OEF and resting CMRO(2) using combined hypercapnia and hyperoxia
title The impact of inspired oxygen levels on calibrated fMRI measurements of M, OEF and resting CMRO(2) using combined hypercapnia and hyperoxia
title_full The impact of inspired oxygen levels on calibrated fMRI measurements of M, OEF and resting CMRO(2) using combined hypercapnia and hyperoxia
title_fullStr The impact of inspired oxygen levels on calibrated fMRI measurements of M, OEF and resting CMRO(2) using combined hypercapnia and hyperoxia
title_full_unstemmed The impact of inspired oxygen levels on calibrated fMRI measurements of M, OEF and resting CMRO(2) using combined hypercapnia and hyperoxia
title_short The impact of inspired oxygen levels on calibrated fMRI measurements of M, OEF and resting CMRO(2) using combined hypercapnia and hyperoxia
title_sort impact of inspired oxygen levels on calibrated fmri measurements of m, oef and resting cmro(2) using combined hypercapnia and hyperoxia
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5376305/
https://www.ncbi.nlm.nih.gov/pubmed/28362834
http://dx.doi.org/10.1371/journal.pone.0174932
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