title: Characteristics of Misclassified CT Perfusion Ischemic Core in Patients with Acute Ischemic Stroke.
abstract: BACKGROUND
  CT perfusion (CTP) is used to estimate the extent of ischemic core and penumbra in patients with acute ischemic stroke. CTP reliability, however, is limited. This study aims to identify regions misclassified as ischemic core on CTP, using infarct on follow-up noncontrast CT. We aim to assess differences in volumetric and perfusion characteristics in these regions compared to areas that ended up as infarct on follow-up.
  
  
  METHODS
  This study included 35 patients with >100 mm brain coverage CTP. CTP processing was performed using Philips software (IntelliSpace 7.0). Final infarct was automatically segmented on follow-up noncontrast CT and used as reference. CTP and follow-up noncontrast CT image data were registered. This allowed classification of ischemic lesion agreement (core on CTP: rMTT≥145%, aCBV<2.0 ml/100g and infarct on follow-up noncontrast CT) and misclassified ischemic core (core on CTP, not identified on follow-up noncontrast CT) regions. False discovery ratio (FDR), defined as misclassified ischemic core volume divided by total CTP ischemic core volume, was calculated. Absolute and relative CTP parameters (CBV, CBF, and MTT) were calculated for both misclassified CTP ischemic core and ischemic lesion agreement regions and compared using paired rank-sum tests.
  
  
  RESULTS
  Median total CTP ischemic core volume was 49.7ml (IQR:29.9ml-132ml); median misclassified ischemic core volume was 30.4ml (IQR:20.9ml-77.0ml). Median FDR between patients was 62% (IQR:49%-80%). Median relative mean transit time was 243% (IQR:198%-289%) and 342% (IQR:249%-432%) for misclassified and ischemic lesion agreement regions, respectively. Median absolute cerebral blood volume was 1.59 (IQR:1.43-1.79) ml/100g (P<0.01) and 1.38 (IQR:1.15-1.49) ml/100g (P<0.01) for misclassified ischemic core and ischemic lesion agreement, respectively. All CTP parameter values differed significantly.
  
  
  CONCLUSIONS
  For all patients a considerable region of the CTP ischemic core is misclassified. CTP parameters significantly differed between ischemic lesion agreement and misclassified CTP ischemic core, suggesting that CTP analysis may benefit from revisions.
authors.affiliation: Dept. of Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Ralph R E G
authors.initials: RR
authors.lastname: Geuskens
authors.affiliation: Dept. of Radiology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Jordi
authors.initials: J
authors.lastname: Borst
authors.affiliation: Dept. of Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Marit
authors.initials: M
authors.lastname: Lucas
authors.affiliation: Dept. of Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: A M Merel
authors.initials: AM
authors.lastname: Boers
authors.affiliation: Dept. of Radiology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Olvert A
authors.initials: OA
authors.lastname: Berkhemer
authors.affiliation: Dept. of Neurology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Yvo B W E M
authors.initials: YB
authors.lastname: Roos
authors.affiliation: Dept. of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Marianne A A
authors.initials: MA
authors.lastname: van Walderveen
authors.affiliation: Dept. of Radiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Sjoerd F M
authors.initials: SF
authors.lastname: Jenniskens
authors.affiliation: Dept. of Radiology, Maastricht University Medical Center+, Maastricht, The Netherlands.
authors.forename: Wim H
authors.initials: WH
authors.lastname: van Zwam
authors.affiliation: Dept. of Neurology, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Diederik W J
authors.initials: DW
authors.lastname: Dippel
authors.affiliation: Dept. of Radiology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Charles B L M
authors.initials: CB
authors.lastname: Majoie
authors.affiliation: Dept. of Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, The Netherlands.|Dept. of Radiology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Henk A
authors.initials: HA
authors.lastname: Marquering
mesh_terms: D001810:Blood Volume; D002545:Brain Ischemia / Q000145:classification* / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D010477:Perfusion; D020521:Stroke / Q000145:classification* / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods*