title: Relative Mean Transit Time Predicts Subsequent Stroke in Symptomatic Carotid Occlusion.
abstract: BACKGROUND
  Mean transit time (MTT) measurements to assess cerebral hemodynamics are easily obtained by computed tomography and magnetic resonance imaging. We reviewed hemodynamic and clinical outcome data from the St. Louis Carotid Occlusion Study to determine if increased MTT was associated with an increased risk of stroke in patients with symptomatic complete carotid artery occlusion.
  
  
  METHODS
  Positron emission tomography (PET) studies of cerebral blood volume-to-cerebral blood flow ratios were used to calculate MTTs. Mean ipsilateral (side of the occluded internal carotid artery)-to-contralateral ratios of MTTs in the middle cerebral artery territories were determined. MTT was tested as a predictor of stroke risk using Cox regression analysis. Receiver operating characteristic curves for stroke risk prediction were generated by varying the mean ispilateral-to-contralateral MTT ratio to identify an optimal cutpoint.
  
  
  RESULTS
  Increased MTT ratio was associated with an increased risk of ipsilateral stroke (P < .001). The maximum combination of sensitivity (.778) and specificity (.763) was obtained at a cutpoint ratio of 1.387 or higher. Subjects with a MTT ratio of 1.387 or higher had a 29.3% 2-year risk of ipsilateral stroke compared to 4.6% for those without (P < .001).
  
  
  CONCLUSIONS
  PET relative MTT ratio identified patients with symptomatic complete internal artery occlusion who were at high risk for subsequent ipsilateral stroke. Confirmation using measurements of relative MTT from other imaging modalities in a patient cohort receiving contemporary medical management is needed.
authors.affiliation: Department of Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri; Department of Radiology, Washington University School of Medicine, St. Louis, Missouri. Electronic address: grubbro@wudosis.wustl.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Grubb
authors.affiliation: Department of Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri; Department of Radiology, Washington University School of Medicine, St. Louis, Missouri; Department of Neurology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Colin P
authors.initials: CP
authors.lastname: Derdeyn
authors.affiliation: Department of Radiology, Washington University School of Medicine, St. Louis, Missouri; Department of Neurology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Tom O
authors.initials: TO
authors.lastname: Videen
authors.affiliation: Department of Neurology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: David A
authors.initials: DA
authors.lastname: Carpenter
authors.affiliation: Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, North Carolina.
authors.forename: William J
authors.initials: WJ
authors.lastname: Powers
mesh_terms: D019540:Area Under Curve; D001783:Blood Flow Velocity; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D016893:Carotid Stenosis / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D006801:Humans; D053208:Kaplan-Meier Estimate; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008923:Missouri; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D012372:ROC Curve; D012039:Regional Blood Flow; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D020521:Stroke / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D013997:Time Factors
keywords: Positron emission tomography; internal carotid artery occlusion; mean transit time; stroke risk