title: Variability of repeated coronary artery calcium measurements on low-dose ECG-gated 16-MDCT.
abstract: OBJECTIVE
  High reproducibility on coronary artery calcium (CAC) scoring is a key requirement in monitoring the progression of coronary atherosclerosis. Retrospective ECG-gated helical CT has been shown to be superior to prospective gating helical CT in the reproducibility of CAC measurements. However, it brings with it a high level of radiation exposure. The purpose of this study was to compare low- and standard-dose protocols in the variability of CAC scores and in image quality, thereby assessing the feasibility of low-dose retrospective ECG-gated helical CT in CAC measurements.
  
  
  METHODS
  Eighty-six patients with CAC were scanned using a tube current setting of 100 mA once and then a tube current setting equivalent to the patient's body weight twice. CAC scores (Agatston and volume) and interscan variability were evaluated. The mean and SD of the CT attenuation values in regions of interest in the aorta were measured, and the value (mean + 2 x SD) was obtained.
  
  
  RESULTS
  A high correlation of log(10) (Agatston score + 1) was observed between sequential helical CT scans (r = 0.998). The variability in CAC measurements ranged from 11% to 12% for both the Agatston and volume scores. With the tube current equivalent to body weight, the value (mean + 2 x SD) did not exceed a CT attenuation value of 130 H.
  
  
  CONCLUSIONS
  Low-dose retrospective ECG-gated helical CT-yielding low variability and achieving the level of image quality needed to measure CAC-can be used to monitor patients with coronary atherosclerosis.
authors.affiliation: Department of Clinical Radiology, Hiroshima University Hospital, 1-2-3, Kasumi-cho, Minami-ku, Hiroshima 734-8551, Japan. horiguch@hiroshima-u.ac.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Horiguchi
authors.forename: Hideya
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Hirai
authors.forename: Yuji
authors.initials: Y
authors.lastname: Akiyama
authors.forename: Chikako
authors.initials: C
authors.lastname: Fujioka
authors.forename: Kazushi
authors.initials: K
authors.lastname: Marukawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fukuda
authors.forename: Katsuhide
authors.initials: K
authors.lastname: Ito
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002114:Calcinosis / Q000000981:diagnostic imaging* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000378:metabolism; D003331:Coronary Vessels / Q000378:metabolism*; D018450:Disease Progression; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D036542:Tomography, Spiral Computed / Q000379:methods
chemical_list: D002118:Calcium