title: Influence of the cardiac cycle on pCASL: cardiac triggering of the end-of-labeling.
abstract: OBJECTIVE
  In arterial spin labeling (ASL), the cardiac cycle might adversely influence signal-stability by varying the amount of label created, labeling efficiency and/or transport times. Due to the long labeling duration in pseudo-Continuous ASL (pCASL), the blood labeled last contributes most to the ASLsignal. The present study investigated, using numerical simulations and in vivo experiments, the effect of the cardiac cycle on pCASL, thereby focusing on the end-of-labeling.
  
  
  METHODS
  In the in vivo experiments the end-of-labeling was timed to a specific cardiac phase while a long labeling duration of >7 s was used to isolate the influence of the lastly labeled spins on ASL-signal stability.
  
  
  RESULTS
  Simulations showed dependence of the ASL-signal on the cardiac phase of the end-of-labeling, and that the variation in signal was more pronounced at lower heart rates. The ASL-signal variation was small (~4%), but could be effectively reduced by simulated end-of-labeling triggering. In vivo, no difference in mean CBF (p = 0.58) nor in CBF temporal-STD (p = 0.44) could be detected between triggered and non-triggered acquisitions.
  
  
  CONCLUSIONS
  Influence of the cardiac cycle on pCASL-signal stability is small and triggering the start-of-labeling and end-of-labeling can be considered not to have practical implications to improve stability.
authors.affiliation: Department of Radiology, C.J. Gorter Center for High Field MRI, Leiden Institute of Brain and Cognition, Leiden University Medical Center, PO-box 9600, 2300 RC, Leiden, The Netherlands. j.verbree@lumc.nl.
authors.forename: Jasper
authors.initials: J
authors.lastname: Verbree
authors.affiliation: Department of Radiology, C.J. Gorter Center for High Field MRI, Leiden Institute of Brain and Cognition, Leiden University Medical Center, PO-box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Matthias J P
authors.initials: MJP
authors.lastname: van Osch
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D002320:Cardiovascular Physiological Phenomena; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D006339:Heart Rate; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D013113:Spin Labels; D055815:Young Adult
chemical_list: D013113:Spin Labels
keywords: Cerebral blood flow; Cerebrovascular circulation; Perfusion magnetic resonance imaging; Pulsatile flow