title: CBF measurements using multidelay pseudocontinuous and velocity-selective arterial spin labeling in patients with long arterial transit delays: comparison with xenon CT CBF.
abstract: OBJECTIVE
  To test the theory that velocity-selective arterial spin labeling (VSASL) is insensitive to transit delay.
  
  
  METHODS
  Cerebral blood flow (CBF) was measured in ten Moyamoya disease patients using xenon computed tomography (xeCT) and magnetic resonance imaging (MRI), which included multiple pseudo-continuous ASL (pcASL) with different postlabel delays, VSASL, and dynamic susceptibility contrast (DSC) imaging. Correlation coefficient, root-mean-square difference, mean CBF error between ASL, and gold-standard xeCT CBF measurements as well the dependence of this error on transit delay (TD) as estimated by DSC time-to-peak of the residue function (Tmax) were determined.
  
  
  RESULTS
  For pcASL with different postlabel delay time (PLD), CBF measurement with short PLD (1.5-2 sec) had the strongest correlations with xeCT; VSASL had a lower but still significant correlation with a mean coefficient of 0.55. We noted the theoretically predicted dependence of CBF error on Tmax and on PLD for pcASL; VSASL CBF measurements had the least dependence of the error on TD. We also noted effects suggesting that the location of the label decay (blood vs. tissue) impacted the measurement, which was worse for pcASL than for VSASL.
  
  
  CONCLUSIONS
  We conclude that VSASL is less sensitive to TD than conventional ASL techniques and holds promise for CBF measurements in cerebrovascular diseases with slow flow.
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Deqiang
authors.initials: D
authors.lastname: Qiu
authors.forename: Matus
authors.initials: M
authors.lastname: Straka
authors.forename: Zungho
authors.initials: Z
authors.lastname: Zun
authors.forename: Roland
authors.initials: R
authors.lastname: Bammer
authors.forename: Michael E
authors.initials: ME
authors.lastname: Moseley
authors.forename: Greg
authors.initials: G
authors.lastname: Zaharchuk
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D003287:Contrast Media; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009072:Moyamoya Disease / Q000473:pathology* / Q000503:physiopathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013113:Spin Labels; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014978:Xenon
chemical_list: D003287:Contrast Media; D013113:Spin Labels; D014978:Xenon