title: Coronary artery calcification measured at electron-beam CT: agreement in dual scan runs and change over time.
abstract: OBJECTIVE
  To use a recently described regression approach to evaluate agreement in the quantity of coronary artery calcification (CAC) with two consecutive acquisitions (dual scan runs) at electron-beam computed tomography (CT) in a quality-control program and to assess the change in CAC quantity over time in an individual.
  
  
  METHODS
  A total of 1,376 asymptomatic research participants, who were not selected because they were at high risk for coronary artery disease, were examined for the quantity of CAC with dual scan runs at electron-beam CT. With these data, 95% limits of agreement were established and used to evaluate differences between scan runs performed approximately 3.5 years apart in 81 participants.
  
  
  RESULTS
  The 95% limits of agreement depended on the mean quantity of CAC in the dual scan runs. Of the 81 participants whose examinations were approximately 3.5 years apart, 59 (73%) had no apparent change in CAC between the two examinations, 21 (26%) had large increases suggesting progression of CAC, and one (1%) had a large decrease suggesting regression of CAC.
  
  
  CONCLUSIONS
  The demonstrated method can be used to evaluate both agreement in dual scan runs and change in quantity of CAC over time.
authors.affiliation: Department of Epidemiology, University of Michigan, Ann Arbor, USA.
authors.forename: L F
authors.initials: LF
authors.lastname: Bielak
authors.forename: P F
authors.initials: PF
authors.lastname: Sheedy
authors.forename: P A
authors.initials: PA
authors.lastname: Peyser
mesh_terms: D002114:Calcinosis / Q000000981:diagnostic imaging*; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011786:Quality Control; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards