title: Strategies of collateral blood flow assessment in ischemic stroke: prediction of the follow-up infarct volume in conventional and dynamic CTA.
abstract: OBJECTIVE
  Collateral blood flow is an important prognostic marker in the acute stroke situation but approaches for assessment vary widely. Our aim was to compare strategies of collateral blood flow assessment in dynamic and conventional CTA in their ability to predict the follow-up infarction volume.
  
  
  METHODS
  We retrospectively included all patients with an M1 occlusion from an existing cohort of 1912 consecutive patients who underwent initial multimodal stroke CT and follow-up MR imaging or nonenhanced CT. Collateralization was assessed in both conventional CT angiography and dynamic CT angiography by using 3 different collateral grading scores and segmentation of the volume of hypoattenuation. Arterial, arteriovenous, and venous phases were reconstructed for dynamic CT angiography, and all collateral scores and the volume of hypoattenuation were individually assessed for all phases. Different grading systems were compared by using the Bayesian information criterion calculated for multivariate regression analyses (Bayesian information criterion difference = 2-6, "positive"; Bayesian information criterion difference = 6-10, "strong"; Bayesian information criterion difference = >10, "very strong").
  
  
  RESULTS
  One hundred thirty-six patients (mean age, 70.4 years; male sex, 41.2%) were included. In the multivariate analysis, models containing the volume of hypoattenuation showed a significantly better model fit than models containing any of the 3 collateral grading scores in conventional CT angiography (Bayesian information criterion difference = >10) and dynamic CT angiography (Bayesian information criterion difference = >10). All grading systems showed the best model fit in the arteriovenous phase. For the volume of hypoattenuation, model fit was significantly higher for models containing the volume of hypoattenuation as assessed in the arteriovenous phase of dynamic CT angiography compared with the venous phase (Bayesian information criterion difference = 6.2) and the arterial phase of dynamic CT angiography (Bayesian information criterion difference = >10) and in comparison with conventional CT angiography (Bayesian information criterion difference = >10).
  
  
  CONCLUSIONS
  The use of dynamic CT angiography within the arteriovenous phase by using quantification of the volume of hypoattenuation is the superior technique for assessment of collateralization among the tested approaches.
authors.affiliation: From the Institute for Clinical Radiology (S.E.B., K.M.T., F.G.M., B.E.-W., M.F.R., W.H.S.).
authors.forename: S E
authors.initials: SE
authors.lastname: Beyer
authors.affiliation: From the Institute for Clinical Radiology (S.E.B., K.M.T., F.G.M., B.E.-W., M.F.R., W.H.S.).
authors.forename: K M
authors.initials: KM
authors.lastname: Thierfelder
authors.affiliation: Departments of Neurology (L.v.B.).
authors.forename: L
authors.initials: L
authors.lastname: von Baumgarten
authors.affiliation: Department of Medical Informatics, Biometry and Epidemiology (M.R.), Ludwig Maximilians University Munich, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Rottenkolber
authors.affiliation: From the Institute for Clinical Radiology (S.E.B., K.M.T., F.G.M., B.E.-W., M.F.R., W.H.S.).
authors.forename: F G
authors.initials: FG
authors.lastname: Meinel
authors.affiliation: Neuroradiology (H.J.), Ludwig Maximilians University Hospital Munich, Munich, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Janssen
authors.affiliation: From the Institute for Clinical Radiology (S.E.B., K.M.T., F.G.M., B.E.-W., M.F.R., W.H.S.).
authors.forename: B
authors.initials: B
authors.lastname: Ertl-Wagner
authors.affiliation: From the Institute for Clinical Radiology (S.E.B., K.M.T., F.G.M., B.E.-W., M.F.R., W.H.S.).
authors.forename: M F
authors.initials: MF
authors.lastname: Reiser
authors.affiliation: From the Institute for Clinical Radiology (S.E.B., K.M.T., F.G.M., B.E.-W., M.F.R., W.H.S.) Wieland.Sommer@med.uni-muenchen.de.
authors.forename: W H
authors.initials: WH
authors.lastname: Sommer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography / Q000379:methods; D001499:Bayes Theorem; D002545:Brain Ischemia / Q000503:physiopathology*; D002544:Cerebral Infarction / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003097:Collateral Circulation / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D020521:Stroke / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed / Q000379:methods