title: Using quantitative CT perfusion for evaluation of delayed cerebral ischemia following aneurysmal subarachnoid hemorrhage.
abstract: OBJECTIVE
  DCI is a serious complication following aneurysmal SAH leading to permanent neurologic deficits, infarction, and death. Our aim was to prospectively evaluate the diagnostic accuracy of CTP and to determine a quantitative threshold for DCI in aneurysmal SAH.
  
  
  METHODS
  Patients with SAH were prospectively enrolled in a protocol approved by the institutional review board. CTP was performed during the typical time period for DCI, between days 6 and 8 following SAH. Quantitative CBF, CBV, and MTT values were obtained by using standard region-of-interest placement sampling of gray matter. The reference standard for DCI is controversial and consisted of clinical and imaging criteria in this study. In a subanalysis of vasospasm, DSA was used as the reference standard. ROC curves determined the diagnostic accuracy by using AUC. Optimal threshold values were calculated by using the patient population utility method.
  
  
  RESULTS
  Ninety-seven patients were included; 41% (40/97) had DCI. Overall diagnostic accuracy was 93% for CBF, 88% for MTT, and 72% for CBV. Optimal threshold values were 35 mL/100 g/min (90% sensitivity, 68% specificity) for CBF and 5.5 seconds (73% sensitivity, 79% specificity) for MTT. In the subanalysis (n = 57), 63% (36/57) had vasospasm. Overall diagnostic accuracy was 94% for CBF, 85% for MTT, and 72% for CBV. Optimal threshold values were 36.5 mL/100 g/min (95% sensitivity, 70% specificity) for CBF and 5.4 seconds (78% sensitivity, 70% specificity) for MTT.
  
  
  CONCLUSIONS
  CBF and MTT have the highest overall diagnostic accuracy. Threshold values of 35 mL/100 g/min for CBF and 5.5-second MTT are suggested for DCI on the basis of the patient population utility method. Absolute threshold values may not be generalizable due to differences in scanner equipment and postprocessing methods.
authors.affiliation: Department of Radiology, New York-Presbyterian Hospital, New York, NY, USA. pcs9001@med.cornell.edu
authors.forename: P C
authors.initials: PC
authors.lastname: Sanelli
authors.forename: I
authors.initials: I
authors.lastname: Ugorec
authors.forename: C E
authors.initials: CE
authors.lastname: Johnson
authors.forename: J
authors.initials: J
authors.lastname: Tan
authors.forename: A Z
authors.initials: AZ
authors.lastname: Segal
authors.forename: M
authors.initials: M
authors.lastname: Fink
authors.forename: L A
authors.initials: LA
authors.lastname: Heier
authors.forename: A J
authors.initials: AJ
authors.lastname: Tsiouris
authors.forename: J P
authors.initials: JP
authors.lastname: Comunale
authors.forename: M
authors.initials: M
authors.lastname: John
authors.forename: P E
authors.initials: PE
authors.lastname: Stieg
authors.forename: R D
authors.initials: RD
authors.lastname: Zimmerman
authors.forename: A I
authors.initials: AI
authors.lastname: Mushlin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000209:etiology*; D002533:Cerebral Angiography / Q000379:methods*; D057210:Delayed Diagnosis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000150:complications* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*