title: Diagnostic threshold values of cerebral perfusion measured with computed tomography for delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.
abstract: OBJECTIVE
  Early diagnosis of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage is critical but difficult. We analyzed diagnostic threshold values of CT perfusion for use in detection of DCI in patients with subarachnoid hemorrhage.
  
  
  METHODS
  We prospectively enrolled patients with subarachnoid hemorrhage with CT perfusion on admission and at time of clinical deterioration or after 1 week if no deterioration occurred. The gold standard was the clinical diagnosis of DCI based on all clinical, laboratory, and imaging data except CT perfusion. Patients with failed imaging (n=6) and other causes of deterioration (n=45) were excluded for the current study. We measured CT perfusion values, including cerebral blood volume, blood flow, mean transit time (MTT), and time to peak in predefined regions of interest and then compared absolute perfusion and perfusion asymmetry for patients with and without DCI. Diagnostic threshold values for DCI were evaluated and sensitivity and specificity calculated for optimal thresholds.
  
  
  RESULTS
  Of 85 eligible patients with subarachnoid hemorrhage, 50 had DCI; 35 patients with no clinical deterioration comprised the reference group. Cerebral blood flow was significantly lower, MTT higher, and perfusion asymmetry larger in patients with DCI. We found that largest absolute MTT and the MTT difference between hemispheres were good diagnostic tests. Diagnostic threshold values with optimal sensitivity and specificity were an MTT of 5.9 seconds and an MTT difference of 1.1 second.
  
  
  CONCLUSIONS
  Thresholds for absolute MTT values and between-hemisphere MTT differences on CT perfusion can distinguish between patients with delayed cerebral ischemia and clinically stable patients.
authors.affiliation: Departments of Radiology, University Medical Center, Utrecht, The Netherlands. j.w.dankbaar@umcutrecht.nl
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: Dankbaar
authors.forename: Nicolien Karen
authors.initials: NK
authors.lastname: de Rooij
authors.forename: Mienke
authors.initials: M
authors.lastname: Rijsdijk
authors.forename: Birgitta K
authors.initials: BK
authors.lastname: Velthuis
authors.forename: Catharine J M
authors.initials: CJ
authors.lastname: Frijns
authors.forename: Gabriel J E
authors.initials: GJ
authors.lastname: Rinkel
authors.forename: Irene C
authors.initials: IC
authors.lastname: van der Schaaf
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D057210:Delayed Diagnosis; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000379:methods*