title: Failure of cerebral hemodynamic selection in general or of specific positron emission tomography methodology?: Carotid Occlusion Surgery Study (COSS).
abstract: OBJECTIVE
  The Carotid Occlusion Surgery Study (COSS) was an improvement over the Extracranial-Intracranial Bypass Study, which did not utilize physiological selection. To assess possible reasons for early closure of the COSS trial, we reviewed COSS methods used to identify high-risk patients and compared results with separate quantitative data.
  
  
  METHODS
  Increased oxygen extraction fraction (OEF) by positron emission tomography is a gold standard for ischemia, but the specific thresholds and equivalency of the semiquantitative OEF ratio utilized in COSS and quantitative OEF are at issue.
  
  
  RESULTS
  The semiquantitative hemispheric OEF ratio used in COSS did not identify the same group of patients as did quantitative OEF using a threshold of 50%.
  
  
  CONCLUSIONS
  The failure of COSS is likely caused by a failure of the semiquantitative, hemispheric OEF ratio method rather than by the selection for bypass based on hemodynamic compromise.
authors.affiliation: Department of Neurosurgery, University of New Mexico, MSC 10 5615, Albuquerque, NM 87131, USA.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Carlson
authors.forename: Howard
authors.initials: H
authors.lastname: Yonas
authors.forename: Yue-Fang
authors.initials: YF
authors.lastname: Chang
authors.forename: Edwin M
authors.initials: EM
authors.lastname: Nemoto
mesh_terms: D002545:Brain Ischemia / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D016893:Carotid Stenosis / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D049268:Positron-Emission Tomography; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D020521:Stroke / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology