title: Optimal perfusion computed tomographic thresholds for ischemic core and penumbra are not time dependent in the clinically relevant time window.
abstract: OBJECTIVE
  This study aims to determine whether perfusion computed tomographic (PCT) thresholds for delineating the ischemic core and penumbra are time dependent or time independent in patients presenting with symptoms of acute stroke.
  
  
  METHODS
  Two hundred seventeen patients were evaluated in a retrospective, multicenter study. Patients were divided into those with either persistent occlusion or recanalization. All patients received admission PCT and follow-up imaging to determine the final ischemic core, which was then retrospectively matched to the PCT images to identify optimal thresholds for the different PCT parameters. These thresholds were assessed for significant variation over time since symptom onset.
  
  
  RESULTS
  In the persistent occlusion group, optimal PCT parameters that did not significantly change with time included absolute mean transit time, relative mean transit time, relative cerebral blood flow, and relative cerebral blood volume when time was restricted to 15 hours after symptom onset. Conversely, the recanalization group showed no significant time variation for any PCT parameter at any time interval. In the persistent occlusion group, the optimal threshold to delineate the total ischemic area was the relative mean transit time at a threshold of 180%. In patients with recanalization, the optimal parameter to predict the ischemic core was relative cerebral blood volume at a threshold of 66%.
  
  
  CONCLUSIONS
  Time does not influence the optimal PCT thresholds to delineate the ischemic core and penumbra in the first 15 hours after symptom onset for relative mean transit time and relative cerebral blood volume, the optimal parameters to delineate ischemic core and penumbra.
authors.affiliation: From the Department of Radiology, Division of Neuroradiology (Y.Q., G.Z., M.W.) and Department of Public Health Sciences (J.P., W.X.), University of Virginia, Charlottesville; Department of Radiology (M.W.) and Department of Neurology (P.M., A.E.), Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland; Military General Hospital of Beijing PLA, Beijing, China (G.Z.); and Department of Neurology, University of Pittsburgh, Pittsburgh, PA (T.J.).
authors.forename: Yujie
authors.initials: Y
authors.lastname: Qiao
authors.forename: Guangming
authors.initials: G
authors.lastname: Zhu
authors.forename: James
authors.initials: J
authors.lastname: Patrie
authors.forename: Wenjun
authors.initials: W
authors.lastname: Xin
authors.forename: Patrik
authors.initials: P
authors.lastname: Michel
authors.forename: Ashraf
authors.initials: A
authors.lastname: Eskandari
authors.forename: Tudor
authors.initials: T
authors.lastname: Jovin
authors.forename: Max
authors.initials: M
authors.lastname: Wintermark
mesh_terms: D000368:Aged; D002545:Brain Ischemia / Q000145:classification / Q000473:pathology / Q000503:physiopathology*; D003287:Contrast Media / Q000008:administration & dosage; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000295:instrumentation / Q000379:methods*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D020521:Stroke / Q000145:classification / Q000473:pathology / Q000503:physiopathology*; D013997:Time Factors; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media
keywords: computed tomography; perfusion imaging; stroke