Feasibility of Estimating CBF/CMRO2 Coupling with a Calibrated-BOLD Method When the Driving Stimulus Is Unknown

Aaron Simon¹, Valerie Griffeth¹, Joanna Perthen¹, Richard Buxton²

The calibrated BOLD method provides a quantitative measurement of CBF/CMRO2 coupling during brain activation. The analysis is typically applied to a region of interest (ROI) selected based on correlation with a known stimulus. We tested the feasibility of using just the coherence of the CBF and BOLD signals measured simultaneously with a dual-echo ASL method to identify an active ROI, with no prior knowledge of the driving stimulus. In human data with a visual stimulus, the CBF/BOLD coherence approach and the standard model correlation approach gave ROI estimates of CBF/CMRO2 coupling that differed by only 7%. This opens the possibility of measuring CBF/CMRO2 coupling with more complex or naturalistic stimuli, supporting a wider range of application of the calibrated-BOLD method.