title: Comparison of pulsed and pseudocontinuous arterial spin-labeling for measuring CO2 -induced cerebrovascular reactivity.
abstract: OBJECTIVE
  To compare the performance of pulsed and pseudocontinuous arterial spin-labeling (PASL and pCASL) methods in measuring CO(2) -induced cerebrovascular reactivity (CVR).
  
  
  METHODS
  Subjects were scanned using both ASL sequences during a controlled hypercapnia procedure and visual stimulation. CVR was computed as the percent CO(2) -induced increase in cerebral blood flow (Δ%CBF) per mmHg increase in end-tidal PCO(2) . Visually evoked responses were expressed as Δ%CBF. Resting CBF and temporal signal-to-noise ratio were also computed. Regionally averaged values for the different quantities were compared in gray matter (GM) and visual cortex (VC) using t-tests.
  
  
  RESULTS
  Both PASL and pCASL yielded comparable respective values for resting CBF (56 ± 3 and 56 ± 4 mL/min/100g) and visually evoked responses (75 ± 5% and 81 ± 4%). Values of CVR determined using pCASL (GM 4.4 ± 0.2, VC 8 ± 1 Δ%CBF/mmHg), however, were significantly higher than those measured using PASL (GM 3.0 ± 0.6, VC 5 ± 1 Δ%CBF/mmHg) in both GM and VC. The percentage of GM voxels in which statistically significant hypercapnia responses were detected was also higher for pCASL (27 ± 5% vs. 16 ± 3% for PASL).
  
  
  CONCLUSIONS
  pCASL may be less prone to underestimation of CO(2) -induced flow changes due to improved label timing control.
authors.affiliation: Institut de génie biomédical, Département de physiologie, Université de Montréal, Montreal, Quebec, Canada. felipe.tancredi@umontreal.ca
authors.forename: Felipe B
authors.initials: FB
authors.lastname: Tancredi
authors.forename: Claudine J
authors.initials: CJ
authors.lastname: Gauthier
authors.forename: Cécile
authors.initials: C
authors.lastname: Madjar
authors.forename: Divya S
authors.initials: DS
authors.lastname: Bolar
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Fisher
authors.forename: Danny J J
authors.initials: DJ
authors.lastname: Wang
authors.forename: Richard D
authors.initials: RD
authors.lastname: Hoge
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D001931:Brain Mapping / Q000379:methods*; D002245:Carbon Dioxide / Q000008:administration & dosage*; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013113:Spin Labels
chemical_list: D013113:Spin Labels; D002245:Carbon Dioxide