Cerebral Blood Flow Measurement Using fMRI and PET: A Cross-Validation Study

Figure 1

(a) The fMRI experimental protocol consisted of 6 randomly presented sessions (baseline, hypercapnia, and 4 levels of visual stimulation). (b) The interleaved BOLD-FAIR sequence was repeated 30 times during each run of 6 minutes, composed of a 1-minute baseline, 3-minute stimulation, and 2-minute baseline period. Scans shaded in grey (1 minute post onset and cessation of stimulation plus first scan in the run) were excluded in percent change calculations to ensure that time-averaged data included only physiological changes in steady state. (c) The basic structure of the BOLD-FAIR sequence consists of 2 BOLD acquisitions (averaged to form 1 BOLD-contrast image) interleaved with 1 slice selective and 1 nonselective ASL acquisition. (d) These 4 acquisitions produce a flow-weighted FAIR image through subtraction and a BOLD image through addition.