title: Effect of X-Ray Attenuation of Arterial Obstructions on Intravenous Thrombolysis and Outcome after Ischemic Stroke.
abstract: OBJECTIVE
  To assess whether the x-ray attenuation of intra-arterial obstruction measured on non-contrast CT in ischemic stroke can predict response to thrombolysis and subsequent functional outcome.
  
  
  METHODS
  The Third International Stroke Trial (IST-3) was a multicenter randomized-controlled trial of intravenous thrombolysis (rt-PA) given within six hours of ischemic stroke. Ethical approval and informed consent were obtained. In a subgroup of 109 IST-3 patients (38 men, median age 82 years), a single reader, masked to all clinical and other imaging data, manually measured x-ray attenuation (Hounsfield Units, HU) on non-contrast CT at the location of angiographically-proven intra-arterial obstructions, pre-randomization and at 24-48 hour follow-up. We calculated change in attenuation between scans. We assessed the impact of pre-randomization arterial obstruction attenuation on six-month functional outcome.
  
  
  RESULTS
  Most arterial obstructions (64/109, 59%) were hyperattenuating (mean 51.0 HU). Compared with control, treatment with rt-PA was associated with a greater, but non-significant, reduction in obstruction attenuation at follow-up (-8.0 HU versus -1.4 HU in patients allocated control, p = 0.117). In multivariable ordinal regression analysis controlled for patient age, stroke severity, location and extent of obstruction, time from stroke onset to baseline scan and rt-PA treatment allocation, the attenuation of pre-randomization arterial obstruction was not independently associated with six-month outcome (odds ratio = 0.99, 95% confidence interval = 0.94-1.03, p = 0.516).
  
  
  CONCLUSIONS
  In ischemic stroke, the x-ray attenuation of the arterial obstruction may decline more rapidly from baseline to 24-48 hours following treatment with thrombolysis but we found no evidence that baseline arterial obstruction attenuation predicts six-month outcome.
authors.affiliation: Division of Neuroimaging Sciences, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom.
authors.forename: Grant
authors.initials: G
authors.lastname: Mair
authors.affiliation: Department of Neuroradiology, Dresden University Stroke Centre, University Hospital, Dresden, Germany.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: von Kummer
authors.affiliation: Westmead Hospital Clinical School and The George Institute for Global Health, University of Sydney, Sydney, Australia.
authors.forename: Richard I
authors.initials: RI
authors.lastname: Lindley
authors.affiliation: Division of Clinical Neurosciences, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom.
authors.forename: Peter A G
authors.initials: PA
authors.lastname: Sandercock
authors.affiliation: Division of Neuroimaging Sciences, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom.
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Wardlaw
mesh_terms: D061605:Administration, Intravenous; D000368:Aged; D001157:Arterial Occlusive Diseases / Q000209:etiology / Q000628:therapy*; D002545:Brain Ischemia / Q000150:complications* / Q000503:physiopathology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D020521:Stroke / Q000150:complications* / Q000503:physiopathology; D015912:Thrombolytic Therapy; D016896:Treatment Outcome; D014964:X-Ray Therapy