title: Effect of heart rate and body mass index on the interscan and interobserver variability of coronary artery calcium scoring at prospective ECG-triggered 64-slice CT.
abstract: OBJECTIVE
  To test the effects of heart rate, body mass index (BMI) and noise level on interscan and interobserver variability of coronary artery calcium (CAC) scoring on a prospective electrocardiogram (ECG)-triggered 64-slice CT.
  
  
  METHODS
  One hundred and ten patients (76 patients with CAC) were scanned twice on prospective ECG-triggered scans. The scan parameters included 120 kV, 82 mAs, a 2.5 mm thickness, and an acquisition center at 45% of the RR interval. The interscan and interobserver variability on the CAC scores (Agatston, volume, and mass) was calculated. The factors affecting the variability were determined by plotting it against heart rate, BMI, and noise level (defined as the standard deviation: SD).
  
  
  RESULTS
  The estimated effective dose was 1.5 +/- 0.2 mSv. The mean heart rate was 63 +/- 12 bpm (range, 44-101 bpm). The patient BMIs were 24.5 +/- 4.5 kg/m(2) (range, 15.5-42.3 kg/m(2)). The mean and median interscan variabilities were 11% and 6%, respectively by volume, and 11% and 6%, respectively, by mass. Moreover, the mean and median of the algorithms were lower than the Agatston algorithm (16% and 9%, respectively). The mean and median interobserver variability was 10% and 4%, respectively (average of algorithms). The mean noise levels were 15 +/- 4 Hounsfield unit (HU) (range, 8-25 HU). The interscan and interobserver variability was not correlated with heart rate, BMI, or noise level.
  
  
  CONCLUSIONS
  The interscan and interobserver variability of CAC on a prospective ECG-triggered 64-slice CT with high image quality and 45% of RR acquisition is not significantly affected by heart rate, BMI, or noise level. The volume or mass algorithms show reduced interscan variability compared to the Agatston scoring (p < 0.05).
authors: Department of Clinical Radiology, Hiroshima University Hospital, Minami-ku, Hiroshima, Japan. horiguch@hiroshima-u.ac.jp
authors: Jun
authors: J
authors: Horiguchi
authors: Noriaki
authors: N
authors: Matsuura
authors: Hideya
authors: H
authors: Yamamoto
authors: Masao
authors: M
authors: Kiguchi
authors: Chikako
authors: C
authors: Fujioka
authors: Toshiro
authors: T
authors: Kitagawa
authors: Katsuhide
authors: K
authors: Ito
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D002118:Calcium / Q000032:analysis*; D017023:Coronary Angiography / Q000379:methods*; D003331:Coronary Vessels / Q000737:chemistry*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D002118:Calcium