title: MRI perfusion maps in acute stroke validated with 15O-water positron emission tomography.
abstract: OBJECTIVE
  Perfusion-weighted imaging maps are used to identify hypoperfusion in acute ischemic stroke. We evaluated maps of cerebral blood flow (CBF), cerebral blood volume, mean transit time, and time to peak (TTP) in acute stroke by comparison with positron emission tomography.
  
  
  METHODS
  Perfusion-weighted imaging and positron emission tomography were performed in 26 patients with acute ischemic stroke (median 18.5 hours after stroke onset, 65 minutes between MRI and positron emission tomography). The perfusion-weighted imaging-derived maps of CBF, cerebral blood volume, mean transit time, and TTP delay were compared with quantitative positron emission tomography CBF. A receiver-operating characteristic curve analysis identified the best perfusion-weighted imaging map and threshold to identify hypoperfusion <20 mL/100 g/min, a widely used measure of penumbral flow.
  
  
  RESULTS
  Individual regression analysis of positron emission tomography CBF and perfusion-weighted imaging values were strong for CBF and TTP delay and weaker for mean transit time and cerebral blood volume, but the pooled analysis showed a large variance. Receiver-operating characteristic curve analysis identified TTP and CBF maps as most predictive (median area under the curve=0.94 and 0.93). Penumbral flow thresholds were <21.7 mL/100 g/min (CBF), <1.5 mL/100 g (cerebral blood volume), >5.3 seconds (mean transit time), and >4.2 seconds (TTP). TTP and CBF maps reached sensitivity/specificity values of 91%/82% and 89%/87%.
  
  
  CONCLUSIONS
  In our sample, maps of CBF, TTP, and mean transit time yielded a good estimate of penumbral flow. The performance of TTP maps was equivalent to deconvolution techniques using an arterial input function. For all maps, the application of a predefined threshold is mandatory and calibration studies will enhance their use in acute stroke therapy as well as in clinical stroke trials.
authors.affiliation: Department of Neurology, University of Cologne, Max Planck Institute for Neurological Research, Gleueler Str 50, 50931 Cologne, Germany. zaroweber@nf.mpg.de
authors.forename: Olivier
authors.initials: O
authors.lastname: Zaro-Weber
authors.forename: Walter
authors.initials: W
authors.lastname: Moeller-Hartmann
authors.forename: Wolf-Dieter
authors.initials: WD
authors.lastname: Heiss
authors.forename: Jan
authors.initials: J
authors.lastname: Sobesky
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D010104:Oxygen Radioisotopes; D055420:Perfusion Imaging / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods; D011446:Prospective Studies; D020521:Stroke / Q000175:diagnosis* / Q000503:physiopathology; D014867:Water; D055815:Young Adult
chemical_list: D010104:Oxygen Radioisotopes; D014867:Water