title: Computed tomography angiography source images closely reflect the integrity of collateral circulation.
abstract: BACKGROUND
  We studied the interplay between collateral circulation, the location of the thrombus and infarct extent based on evaluation of CT angiography source images (CTA-SI) in predicting the clinical outcome of patients treated with intravenous thrombolytic therapy (<3h) in a retrospective cohort.
  
  
  METHODS
  Anterior circulation occlusion was detected with CTA in 105 patients. The site of the occlusion was recorded, collaterals were assessed with Collateral Score (CS) and Alberta Stroke Program Early CT Score (ASPECTS) was evaluated from CTA-SI, and entered into logistic regression analysis to predict favorable clinical outcome (three-month modified Rankin Scale 0-2).
  
  
  RESULTS
  CTA-SI ASPECTS was highly correlated with CS (Spearman's rho=0.63, P=0.01). Not a single patient with good collaterals (CS 2-4) had a poor CTA-SI scan (ASPECTS 0-7). The mean CTA-SI ASPECTS score became progressively lower when the status of the collateral circulation deteriorated (ANOVA P<0.001). In univariate analysis a good CTA-SI scan at the admission predicted favorable three-month outcome (P<0.001). In a multivariate model containing CTA-SI ASPECTS, CS and the site of the occlusion along with significant clinical parameters, CTA-SI ASPECTS was rendered non-significant (P=0.43) in the presence of CS.
  
  
  CONCLUSIONS
  CTA-SI and CS convey overlapping information. CTA-SI is not a significant predictor of the clinical outcome three months after intravenous thrombolysis when the other CTA-based parameters, CS and the clot location, are considered simultaneously. CTA-SI may have a role in the assessment of the extent of irreversible ischemic changes at admission if contrast injection and image acquisition protocols are designed suitably.
authors.affiliation: Medical Imaging Center, Tampere University Hospital, PL 2000, 33521 Tampere, Finland. Electronic address: niko.sillanpaa@pshp.fi.
authors.forename: Niko
authors.initials: N
authors.lastname: Sillanpää
authors.affiliation: Department of Neurology, University of Tampere, Tampere and Vaasa Central Hospital, Vaasa, Finland.
authors.forename: Jukka Tapio
authors.initials: JT
authors.lastname: Saarinen
authors.affiliation: Department of Neurology, Oulu University Hospital, Oulu, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Rusanen
mesh_terms: D000368:Aged; D002536:Cerebral Arteries / Q000000981:diagnostic imaging*; D003097:Collateral Circulation; D005260:Female; D005343:Fibrinolytic Agents / Q000627:therapeutic use; D006801:Humans; D008297:Male; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D020521:Stroke / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D015912:Thrombolytic Therapy; D016896:Treatment Outcome
chemical_list: D005343:Fibrinolytic Agents
keywords: Collateral circulation; Computed tomography angiography source images; Middle cerebral artery occlusion; Stroke; Thrombolysis