title: Improved reproducibility of coronary artery calcium scoring by electron beam tomography with a new electrocardiographic trigger method.
abstract: OBJECTIVE
  To improve the interscan reproducibility with electron beam tomography (EBT) by choosing an optimal electrocardiographic (ECG) trigger time.
  
  
  METHODS
  Two hundred fourteen asymptomatic subjects found to have coronary artery calcium (CAC) on EBT were rescanned immediately to measure the interscan variability. Subjects were randomized to one of two different ECG trigger interval groups: the new trigger method (group 1) and the 80% R-R interval trigger method (group 2). The new trigger method was derived from a previous study of motion in the coronary arteries. In group 1 (new trigger method), the ECG trigger was programmed for a certain time (in ms) after the R wave, based on the resting heart rate. The triggers for group 1 were 360 (heart rate <50 beats per minute [bpm]), 340 (51--60 bpm), 314 (61--70 bpm), 300 (71--80 bpm), 290 (81--90 bpm), 280 (91--100 bpm), and 270 ms (>100 bpm). The interscan variation (CAC area and Agatston score) was compared between the two groups.
  
  
  RESULTS
  The interscan variability was significantly reduced using the new trigger method for both CAC area and score compared with the 80% trigger method. The individual lesion variation was also significantly reduced by the new trigger method compared with the 80% trigger method. Area measure had a significantly lower variability compared with the Agatston score.
  
  
  CONCLUSIONS
  These results strongly support the use of this new ECG trigger that relies on a rate-adjusted millisecond delay after the R wave instead of the more commonly used 80% R-R interval in EBT calcium studies.
authors.affiliation: Harbor-UCLA Research and Education Institute, Torrance, California 90502, USA.
authors.forename: S
authors.initials: S
authors.lastname: Mao
authors.forename: M J
authors.initials: MJ
authors.lastname: Budoff
authors.forename: H
authors.initials: H
authors.lastname: Bakhsheshi
authors.forename: S C
authors.initials: SC
authors.lastname: Liu
mesh_terms: D016477:Artifacts; D002114:Calcinosis / Q000000981:diagnostic imaging*; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*