title: Coronary artery calcium: a multi-institutional, multimanufacturer international standard for quantification at cardiac CT.
abstract: OBJECTIVE
  To develop a consensus standard for quantification of coronary artery calcium (CAC).
  
  
  METHODS
  A standard for CAC quantification was developed by a multi-institutional, multimanufacturer international consortium of cardiac radiologists, medical physicists, and industry representatives. This report specifically describes the standardization of scan acquisition and reconstruction parameters, the use of patient size-specific tube current values to achieve a prescribed image noise, and the use of the calcium mass score to eliminate scanner- and patient size-based variations. An anthropomorphic phantom containing calibration inserts and additional phantom rings were used to simulate small, medium-size, and large patients. The three phantoms were scanned by using the recommended protocols for various computed tomography (CT) systems to determine the calibration factors that relate measured CT numbers to calcium hydroxyapatite density and to determine the tube current values that yield comparable noise values. Calculation of the calcium mass score was standardized, and the variance in Agatston, volume, and mass scores was compared among CT systems.
  
  
  RESULTS
  Use of the recommended scanning parameters resulted in similar noise for small, medium-size, and large phantoms with all multi-detector row CT scanners. Volume scores had greater interscanner variance than did Agatston and calcium mass scores. Use of a fixed calcium hydroxyapatite density threshold (100 mg/cm(3)), as compared with use of a fixed CT number threshold (130 HU), reduced interscanner variability in Agatston and calcium mass scores. With use of a density segmentation threshold, the calcium mass score had the smallest variance as a function of patient size.
  
  
  CONCLUSIONS
  Standardized quantification of CAC yielded comparable image noise, spatial resolution, and mass scores among different patient sizes and different CT systems and facilitated reduced radiation dose for small and medium-size patients.
authors: Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA. mccollough.cynthia@mayo.edu
authors: Cynthia H
authors: CH
authors: McCollough
authors: Stefan
authors: S
authors: Ulzheimer
authors: Sandra S
authors: SS
authors: Halliburton
authors: Kaiss
authors: K
authors: Shanneik
authors: Richard D
authors: RD
authors: White
authors: Willi A
authors: WA
authors: Kalender
mesh_terms: D002114:Calcinosis / Q000000981:diagnostic imaging*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D006801:Humans; D007221:Industry / Q000592:standards*; D007391:International Cooperation; D019047:Phantoms, Imaging / Q000592:standards*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000592:standards*