title: Quantitative mapping of cerebrovascular reactivity using resting-state BOLD fMRI: Validation in healthy adults.
abstract: In conventional neuroimaging, cerebrovascular reactivity (CVR) is quantified primarily using the blood-oxygenation level-dependent (BOLD) functional MRI (fMRI) signal, specifically, as the BOLD response to intravascular carbon dioxide (CO2) modulations, in units of [%ΔBOLD/mmHg]. While this method has achieved wide appeal and clinical translation, the tolerability of CO2-related tasks amongst patients and the elderly remains a challenge in more routine and large-scale applications. In this work, we propose an improved method to quantify CVR by exploiting intrinsic fluctuations in CO2 and corresponding changes in the resting-state BOLD signal (rs-qCVR). Our rs-qCVR approach requires simultaneous monitoring of PETCO2, cardiac pulsation and respiratory volume. In 16 healthy adults, we compare our quantitative CVR estimation technique to the prospective CO2-targeting based CVR quantification approach (qCVR, the "standard"). We also compare our rs-CVR to non-quantitative alternatives including the resting-state fluctuation amplitude (RSFA), amplitude of low-frequency fluctuation (ALFF) and global-signal regression. When all subjects were pooled, only RSFA and ALFF were significantly associated with qCVR. However, for characterizing regional CVR variations within each subject, only the PETCO2-based rs-qCVR measure is strongly associated with standard qCVR in 100% of the subjects (p≤0.1). In contrast, for the more qualitative CVR measures, significant within-subject association with qCVR was only achieved in 50-70% of the subjects. Our work establishes the feasibility of extracting quantitative CVR maps using rs-fMRI, opening the possibility of mapping functional connectivity and qCVR simultaneously.
authors.affiliation: Rotman Research Institute, Baycrest Centre, Canada.
authors.forename: Ali M
authors.initials: AM
authors.lastname: Golestani
authors.affiliation: Rotman Research Institute, Baycrest Centre, Canada; Department of Physics and Astronomy, University of British Columbia, Canada.
authors.forename: Luxi L
authors.initials: LL
authors.lastname: Wei
authors.affiliation: Rotman Research Institute, Baycrest Centre, Canada; Department of Medical Biophysics, University of Toronto, Canada. Electronic address: jchen@research.baycrest.org.
authors.forename: J Jean
authors.initials: JJ
authors.lastname: Chen
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002245:Carbon Dioxide / Q000493:pharmacokinetics*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000097:blood; D015203:Reproducibility of Results; D012146:Rest / Q000502:physiology; D012680:Sensitivity and Specificity; D014664:Vasodilation / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen
keywords: Cerebrovascular reactivity; Deconvolution; End-tidal CO(2); Heart-rate variability; Hemodynamic response function; Non-invasive vascular mapping; Respiratory-volume variability; Resting-state fMRI