title: A standardized method for measuring intracranial arterial stenosis.
abstract: OBJECTIVE
  Atherosclerosis of the major intracranial arteries is an important cause of ischemic stroke. We established measurement criteria to assess percent stenosis of a major intracranial artery (carotid, middle cerebral, vertebral, basilar) and determined the interobserver/intraobserver agreements and interclass/intraclass correlations of these measurements.
  
  
  METHODS
  We defined percent stenosis of an intracranial artery as follows: percent stenosis = [(1 - (D(stenosis)/D(normal)))] x 100, where D(stenosis) = the diameter of the artery at the site of the most severe stenosis and D(normal) = the diameter of the proximal normal artery. If the proximal segment was diseased, contingency sites were chosen to measure D(normal): distal artery (second choice), feeding artery (third choice). Using a hand-held digital caliper, three neuroradiologists independently measured D(stenosis) and D(normal) of 24 stenotic intracranial arteries. Each observer repeated the readings 4 weeks later. We determined how frequently two observers' measurements of percent stenosis of each of the 24 diseased arteries differed by 10% or less.
  
  
  RESULTS
  Among the three pairs of observers, interobserver agreements were 88% (observer 1 versus observer 2), 79% (observer 1 versus observer 3), 75% (observer 2 versus observer 3) for the first reading and were 75% (observer 1 versus observer 2), 100% (observer 1 versus observer 3), and 71% (observer 2 versus observer 3) for the second reading. Intraobserver agreement for each of the observers was 88%, 83%, and 100%. Interclass correlation was 85% (first reading) and 87% (second reading). Intraclass correlation was 92% (first and second readings combined).
  
  
  CONCLUSIONS
  This method shows good interobserver and intraobserver agreements for the measurement of intracranial stenosis of a major artery. If validated in subsequent studies, this method may serve as a standard for the measurement of percent stenosis of an intracranial artery.
authors.affiliation: Department of Neurology, Emory University, Atlanta, GA 30322, USA.
authors.forename: O B
authors.initials: OB
authors.lastname: Samuels
authors.forename: G J
authors.initials: GJ
authors.lastname: Joseph
authors.forename: M J
authors.initials: MJ
authors.lastname: Lynn
authors.forename: H A
authors.initials: HA
authors.lastname: Smith
authors.forename: M I
authors.initials: MI
authors.lastname: Chimowitz
mesh_terms: D001157:Arterial Occlusive Diseases / Q000473:pathology*; D016893:Carotid Stenosis / Q000473:pathology*; D002536:Cerebral Arteries / Q000473:pathology*; D006801:Humans; D015588:Observer Variation; D015203:Reproducibility of Results; D014715:Vertebrobasilar Insufficiency / Q000473:pathology*