title: Ischemic stroke in evolution: predictive value of perfusion computed tomography.
abstract: BACKGROUND
  Various perfusion computed tomography (PCT) parameters have been used to identify tissue at risk of infarction in the setting of acute stroke. The purpose of this study was to examine predictive value of the PCT parameters commonly used in clinical practice to define ischemic penumbra. The patient selection criterion aimed to exclude the effect of thrombolysis from the imaging data.
  
  
  METHODS
  Consecutive acute stroke patients were screened and a total of 18 patients who initially underwent PCT and CT angiogram (CTA) on presentation but did not qualify to receive thrombolytic therapy were selected. The PCT images were postprocessed using a delay-sensitive deconvolution algorithm. All the patients had follow-up noncontrast CT or magnetic resonance imaging to delineate the extent of their infarction. The extent of lesions on PCT maps calculated from mean transit time (MTT), time to peak (TTP), cerebral blood flow, and cerebral blood volume were compared and correlated with the final infarct size. A collateral grading score was used to measure collateral blood supply on the CTA studies.
  
  
  RESULTS
  The average size of MTT lesions was larger than infarct lesions (P < .05). The correlation coefficient of TTP/infarct lesions (r = .95) was better than MTT/infarct lesions (r = .66) (P = .004).
  
  
  CONCLUSIONS
  A widely accepted threshold to define MTT lesions overestimates the ischemic penumbra. In this setting, TTP with appropriate threshold is a better predictor of infarct in acute stroke patients. The MTT/TTP mismatch correlates with the status of collateral blood supply to the tissue at risk of infarction.
authors: Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, Maryland. Electronic address: akherad@jhu.edu.
authors: Amir
authors: A
authors: Kheradmand
authors: Department of Neurology, University of Massachusetts Medical School, Worcester, Massachusetts.
authors: Marc
authors: M
authors: Fisher
authors: Department of Neurology, University of Massachusetts Medical School, Worcester, Massachusetts.
authors: David
authors: D
authors: Paydarfar
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002533:Cerebral Angiography; D002560:Cerebrovascular Circulation; D003097:Collateral Circulation; D018450:Disease Progression; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012720:Severity of Illness Index; D020521:Stroke / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013997:Time Factors; D014057:Tomography, X-Ray Computed
keywords: Computed tomography; mean transit time; perfusion; stroke; time to peak