Paper Info
Title
Improved fMRI calibration: Precisely controlled hyperoxic versus hypercapnic stimuli.
Abstract
The calibration of functional magnetic resonance imaging (fMRI) for the estimation of neuronal activation-induced changes in cerebral metabolic rate of oxygen (CMRO2) has been achieved through hypercapnic-induced iso-metabolic increases in cerebral blood flow (CBF). Hypercapnia (HC) has been traditionally implemented through alterations in the fixed inspired fractional concentrations of carbon dioxide (FICO2) without otherwise controlling end-tidal partial pressures of carbon dioxide (PETCO2) or oxygen (PETO2). There are several shortcomings to the use of this manual HC method that may be improved by using precise targeting of PETCO2 while maintaining iso-oxia. Similarly, precise control of blood gases can be used to induce isocapnic hyperoxia (HO) to reduce venous deoxyhaemoglobin (dHb) and thus increase BOLD signals, without appreciably altering CMRO2 or CBF. The aim of our study was to use precise end-tidal targeting to compare the calibration of BOLD signals under an isocapnic hyperoxic protocol (HOP) (rises in PETO2 to 140, 240 and 340mmHg from baseline) to that of an iso-oxic hypercapnic protocol (HCP) (rises in PETCO2 of 3, 5, 7 and 9mmHg from baseline). Nine healthy volunteers were imaged at 3T while monitoring end-tidal gas concentrations and simultaneously measuring BOLD and CBF signals, via arterial spin labeling (ASL), during graded HCP and HOP, alternating with normocapnic states in a blocked experimental design. The variability of the calibration constant obtained under HOP (MHOP) was 0.3–0.5 that of the HCP one (MHCP). In addition, M-variances with precise gas targeting (MHCP and MHOP) were less than those reported in studies using traditional FICO2 and FIO2 methods (MHC and MHO, respectively). We conclude that precise controlled gas delivery markedly improves BOLD-calibration for fMRI studies of oxygen metabolism with both the HCP and the more precise HOP-alternative.
Year
DOI
Venue
2011
10.1016/j.neuroimage.2010.08.070
NeuroImage
Keywords
Field
DocType
fMRI,Computer-controlled respiratory actuator,Hypercapnia,Hyperoxia,BOLD-calibration,Cerebral blood flow
Partial pressure,Biomedical engineering,Functional magnetic resonance imaging,Oxygen,Hyperoxia,Anesthesia,Psychology,Site-directed spin labeling,Cognitive psychology,Hypercapnia,Cerebral blood flow,Magnetic resonance imaging
Journal
Volume
Issue
ISSN
54
2
1053-8119
Citations 
PageRank 
References 
29
1.26
10
Authors
3
Name
Order
Citations
PageRank
Clarisse I. Mark1311.66
joseph a fisher21410264.50
G Bruce Pike3699132.31