title: Thrombus length estimation in acute ischemic stroke: a potential role for delayed contrast enhanced CT.
abstract: OBJECTIVE
  Thrombus length has been shown to be an important determinant of recanalization using intravenous thrombolysis in hyperacute ischemic stroke. Various studies have attempted to quantify thrombus based on non-contrast CT (NCCT) or CT angiography (CTA). However, thrombus may not be seen on NCCT, and CTA may fail to delineate the distal extent of the thrombus. Contrast enhanced CT (CECT) following CTA can be used to estimate infarct core, but we investigated whether the angiographic data available on these images provided reliable information on thrombus length.
  
  
  METHODS
  15 consecutive patients, mean age 81 years (range 63-93), with terminal internal carotid artery or M1-middle cerebral artery occlusions underwent NCCT, CTA (bolus tracked technique), and CECT (acquired 80 s post initial CTA injection). Three radiologists assessed thrombus length on thin slice NCCT, and CTA and CECT.
  
  
  RESULTS
  CTA overestimated thrombus length relative to NCCT (p<0.001) and CECT (p<0.001). There was less difference between CTA and CECT estimation in patients with good collateral scores (p<0.05). There was good correlation between NCCT and CECT (Pearson's correlation coefficient=0.90, 95% CI 0.81 to 0.95, p<0.001). Inter-rater reliability assessed using intraclass correlation was 0.95 (95% CI 0.87 to 0.98) for NCCT and 0.98 (95% CI 0.94 to 0.99) for CECT.
  
  
  CONCLUSIONS
  CTA regularly overestimates thrombus length as the distal end of the thrombus is not delineated. This can be overcome through the use of a CECT acquisition which can reliably be used to estimate thrombus length.
authors.affiliation: Department of Neuroradiology, Frenchay Hospital, Bristol, UK.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Mortimer
authors.forename: David H
authors.initials: DH
authors.lastname: Little
authors.forename: Kishore S
authors.initials: KS
authors.lastname: Minhas
authors.forename: Edward Rj
authors.initials: ER
authors.lastname: Walton
authors.forename: Shelley A
authors.initials: SA
authors.lastname: Renowden
authors.forename: Marcus D
authors.initials: MD
authors.lastname: Bradley
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000209:etiology; D002340:Carotid Artery Diseases / Q000150:complications; D002533:Cerebral Angiography / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D005260:Female; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000150:complications; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D015203:Reproducibility of Results; D020521:Stroke / Q000000981:diagnostic imaging* / Q000209:etiology; D013927:Thrombosis / Q000000981:diagnostic imaging*
keywords: Artery; CT; CT Angiography; Stroke; Thrombolysis