title: Electron-beam CT: use of a calibration phantom to reduce variability in calcium quantitation.
abstract: OBJECTIVE
  To measure scanner and patient variation in computed tomographic (CT) numbers for electron-beam CT and to determine the ability of calibration phantoms to reduce variability in calcium quantitation.
  
  
  METHODS
  Two calibration phantoms were imaged to ensure longitudinal homogeneity and to determine the short-term intrascanner variation in CT numbers. Each phantom set was imaged twice a day for 14 weeks to determine intra- and interscanner variation. Data from examinations of 167 patients that included the phantom were analyzed to determine the intra- and interpatient variation in CT numbers of objects with known calcium concentrations.
  
  
  RESULTS
  The calibration reduced scanner variations by approximately 25%. The calcium concentration associated with a CT number of 130 HU varied from 77.1 to 136.4 mg/cm3 and was dependent on patient girth, sex, smoking history, and image level.
  
  
  CONCLUSIONS
  Scanner and patient variations in CT numbers in electron-beam CT can be reduced with a calibration phantom. In vitro and in vivo estimates of calcium concentration had a precision of 2% and 7%, respectively.
authors.affiliation: Department of Diagnostic Radiology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: McCollough
authors.forename: R B
authors.initials: RB
authors.lastname: Kaufmann
authors.forename: B M
authors.initials: BM
authors.lastname: Cameron
authors.forename: D J
authors.initials: DJ
authors.lastname: Katz
authors.forename: P F
authors.initials: PF
authors.lastname: Sheedy
authors.forename: P A
authors.initials: PA
authors.lastname: Peyser
mesh_terms: D000328:Adult; D002114:Calcinosis / Q000000981:diagnostic imaging*; D002138:Calibration; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008961:Models, Structural; D014057:Tomography, X-Ray Computed