title: Implication of cerebral circulation time in intracranial stenosis measured by digital subtraction angiography on cerebral blood flow estimation measured by arterial spin labeling.
abstract: OBJECTIVE
  Arterial spin labeling (ASL) magnetic resonance imaging to assess cerebral blood flow (CBF) is of increasing interest in basic research and in diagnostic applications, since ASL provides similar information to positron emission tomography about perfusion in vascular territories. However, in patients with steno-occlusive arterial disease (SOAD), CBF as measured by ASL might be underestimated due to delayed bolus arrival, and thus increased spin relaxation. We aimed to estimate the extent to which bolus arrival time (BAT) was delayed in patients with SOAD and whether this resulted in underestimation of CBF.
  
  
  METHODS
  BAT was measured using digital subtraction angiography (DSA) in ten patients with high-grade stenosis of the middle carotid artery (MCA). Regional CBF was assessed with pseudocontinuous ASL.
  
  
  RESULTS
  BATs were nonsignificantly prolonged in the stenotic hemisphere 4.1±2.0 s compared with the healthy hemisphere 3.3±0.9 s; however, there were substantial individual differences on the stenotic side. CBF in the anterior and posterior MCA territories were significantly reduced on the stenotic hemisphere. Severe stenosis was correlated with longer BAT and lower quantified CBF.
  
  
  CONCLUSIONS
  ASL-based perfusion measurement involves a race between the decay of the spins and the delivery of labeled blood to the region of interest. Special caution is needed when interpreting CBF values quantified in individuals with altered blood flow and delayed circulation times. However, from a clinician's point of view, an accentuation of hypoperfusion (even if caused by underestimation of CBF due to prolonged BATs) might be desirable since it indexes potentially harmful physiologic deficits.
authors.affiliation: Department of Psychiatric Neurophysiology, University Hospital of Psychiatry and University of Bern, Bern, Switzerland. jann@puk.unibe.ch.
authors.forename: Kay
authors.initials: K
authors.lastname: Jann
authors.forename: Martinus
authors.initials: M
authors.lastname: Hauf
authors.forename: Frauke
authors.initials: F
authors.lastname: Kellner Weldon
authors.forename: Marwan
authors.initials: M
authors.lastname: El Koussy
authors.forename: Claus
authors.initials: C
authors.lastname: Kiefer
authors.forename: Andrea
authors.initials: A
authors.lastname: Federspiel
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schroth
mesh_terms: D000328:Adult; D000368:Aged; D015901:Angiography, Digital Subtraction / Q000379:methods*; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging; D002560:Cerebrovascular Circulation; D003251:Constriction, Pathologic; D005260:Female; D006801:Humans; D020765:Intracranial Arterial Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D013113:Spin Labels
chemical_list: D013113:Spin Labels