title: Different CT perfusion algorithms in the detection of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.
abstract: BACKGROUND
  Tracer delay-sensitive perfusion algorithms in CT perfusion (CTP) result in an overestimation of the extent of ischemia in thromboembolic stroke. In diagnosing delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH), delayed arrival of contrast due to vasospasm may also overestimate the extent of ischemia. We investigated the diagnostic accuracy of tracer delay-sensitive and tracer delay-insensitive algorithms for detecting DCI.
  
  
  METHODS
  From a prospectively collected series of aSAH patients admitted between 2007-2011, we included patients with any clinical deterioration other than rebleeding within 21 days after SAH who underwent NCCT/CTP/CTA imaging. Causes of clinical deterioration were categorized into DCI and no DCI. CTP maps were calculated with tracer delay-sensitive and tracer delay-insensitive algorithms and were visually assessed for the presence of perfusion deficits by two independent observers with different levels of experience. The diagnostic value of both algorithms was calculated for both observers.
  
  
  RESULTS
  Seventy-one patients were included. For the experienced observer, the positive predictive values (PPVs) were 0.67 for the delay-sensitive and 0.66 for the delay-insensitive algorithm, and the negative predictive values (NPVs) were 0.73 and 0.74. For the less experienced observer, PPVs were 0.60 for both algorithms, and NPVs were 0.66 for the delay-sensitive and 0.63 for the delay-insensitive algorithm.
  
  
  CONCLUSIONS
  Test characteristics are comparable for tracer delay-sensitive and tracer delay-insensitive algorithms for the visual assessment of CTP in diagnosing DCI. This indicates that both algorithms can be used for this purpose.
authors.affiliation: Department of Neurology and Neurosurgery, Room G03.232, Brain Center Rudolf Magnus Department of Neurology and Neurosurgery, University Medical Center Utrecht, PO Box 85500, 3508 GA, Utrecht, The Netherlands, c.h.p.cremers-2@umcutrecht.nl.
authors.forename: Charlotte H P
authors.initials: CH
authors.lastname: Cremers
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: Dankbaar
authors.forename: Mervyn D I
authors.initials: MD
authors.lastname: Vergouwen
authors.forename: Pieter C
authors.initials: PC
authors.lastname: Vos
authors.forename: Edwin
authors.initials: E
authors.lastname: Bennink
authors.forename: Gabriel J E
authors.initials: GJ
authors.lastname: Rinkel
authors.forename: Birgitta K
authors.initials: BK
authors.lastname: Velthuis
authors.forename: Irene C
authors.initials: IC
authors.lastname: van der Schaaf
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging / Q000379:methods*; D011446:Prospective Studies; D015203:Reproducibility of Results; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000503:physiopathology; D013997:Time Factors; D014057:Tomography, X-Ray Computed