title: Pseudocontinuous arterial spin labeling quantifies relative cerebral blood flow in acute stroke.
abstract: OBJECTIVE
  The aim of this study was to test whether arterial spin labeling (ASL) can detect significant differences in relative cerebral blood flow (rCBF) in the core, mismatch, and reverse-mismatch regions, and whether rCBF values measured by ASL in those areas differ from values obtained using dynamic susceptibility contrast (DSC) MRI.
  
  
  METHODS
  Acute stroke patients were imaged with diffusion-weighted imaging (DWI) and perfusion-weighted imaging (ASL and DSC) MRI. An expert reader segmented the ischemic lesion on DWI and the DSC time-to-peak (TTP) maps. Three regions were defined: core (DWI+, TTP+), mismatch (DWI-, TTP+), and reverse-mismatch (DWI+, TTP-). For both ASL and DSC, rCBF maps were created with commercially available software, and the ratio was calculated as the mean signal intensity measured on the side of the lesion to that of the homologous region in the contralateral hemisphere. Values obtained from core, mismatch, and reverse-mismatch were used for paired comparison.
  
  
  RESULTS
  Twenty-eight patients were included in the study. The mean age was 65.6 (16.9) years, with a median baseline National Institutes of Health Stroke Scale score of 10 (interquartile range, 4-17). Median time from last known normal to MRI was 5.7 hours (interquartile range, 2.9-22.6). Mean rCBF ratios were significantly higher in the mismatch 0.53 (0.23) versus the core 0.39 (0.33) and reverse-mismatch 0.68 (0.49) versus the core 0.38 (0.35). Differences in rCBF measured with DSC and ASL were not significant.
  
  
  CONCLUSIONS
  ASL allows for the measurement of rCBF in the core and mismatch regions. Values in the mismatch were significantly higher than in the core, suggesting there is potential salvageable tissue.
authors.affiliation: Section on Stroke Diagnostics and Therapeutics, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1063, USA.
authors.forename: Daymara A
authors.initials: DA
authors.lastname: Hernandez
authors.forename: Reinoud P H
authors.initials: RP
authors.lastname: Bokkers
authors.forename: Raymond V
authors.initials: RV
authors.lastname: Mirasol
authors.forename: Marie
authors.initials: M
authors.lastname: Luby
authors.forename: Erica C
authors.initials: EC
authors.lastname: Henning
authors.forename: José G
authors.initials: JG
authors.lastname: Merino
authors.forename: Steven
authors.initials: S
authors.lastname: Warach
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Latour
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002152:Calorimetry, Differential Scanning; D002536:Cerebral Arteries / Q000473:pathology / Q000503:physiopathology; D002555:Cerebrospinal Fluid / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D038524:Diffusion Magnetic Resonance Imaging; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005260:Female; D005343:Fibrinolytic Agents / Q000627:therapeutic use; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010477:Perfusion; D012189:Retrospective Studies; D013113:Spin Labels; D020521:Stroke / Q000188:drug therapy / Q000503:physiopathology*; D010959:Tissue Plasminogen Activator / Q000627:therapeutic use
chemical_list: D005343:Fibrinolytic Agents; D013113:Spin Labels; D010959:Tissue Plasminogen Activator