title: CT after subarachnoid hemorrhage: relation of cerebral perfusion to delayed cerebral ischemia.
abstract: BACKGROUND
  Delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH) is difficult to predict. The authors studied the relation between several parameters of brain perfusion at admission and development of DCI.
  
  
  METHODS
  The authors analyzed the admission CT perfusion (CTP) scans of 46 patients scanned within 72 hours after SAH. They assessed cerebral blood volume (CBV) and flow (CBF), mean transit time (MTT), and time to peak (TTP) for eight predefined regions of interest. For patients with and without DCI, the authors compared perfusion quantitatively and semiquantitatively. With receiver-operator characteristic (ROC) curves, the authors assessed the relationship between DCI and perfusion parameters. To assess the potential prognostic value, they calculated sensitivity and specificity of optimal threshold values for the semiquantitative data.
  
  
  RESULTS
  DCI was not significantly related with quantitative perfusion values. For the semiquantitative data, patients with DCI had significantly more asymmetry in perfusion, and ROC curves indicated a good relation (0.75 to 0.81). Optimal threshold values distinguishing between patients with and without DCI were 0.77 for CBV and 0.72 for CBF ratios, and 0.87 seconds for MTT and 1.0 second for TTP differences. The corresponding sensitivity was 0.75 for all parameters; the specificity was 0.70 for CBV, 0.93 for CBF, 0.70 for MTT, and 0.90 for TTP.
  
  
  CONCLUSIONS
  Delayed cerebral ischemia (DCI) is related to perfusion asymmetry on admission CT perfusion (CTP). The cerebral blood flow ratio (comparing contralateral regions of interest) seems the best prognosticator for development of DCI. Further studies are needed to investigate the additional value of CTP to other prognosticators for DCI and to validate the chosen threshold values.
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, The Netherlands. i.vanderschaaf@rrr.azu.nl
authors.forename: I
authors.initials: I
authors.lastname: van der Schaaf
authors.forename: M J
authors.initials: MJ
authors.lastname: Wermer
authors.forename: Y
authors.initials: Y
authors.lastname: van der Graaf
authors.forename: R G
authors.initials: RG
authors.lastname: Hoff
authors.forename: G J E
authors.initials: GJ
authors.lastname: Rinkel
authors.forename: B K
authors.initials: BK
authors.lastname: Velthuis
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging*; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000209:etiology; D002533:Cerebral Angiography / Q000379:methods*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000150:complications / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013997:Time Factors; D014057:Tomography, X-Ray Computed