title: Ability of calibration phantom to reduce the interscan variability in electron beam computed tomography.
abstract: OBJECTIVE
  To test the hypothesis that a calibration phantom would improve interpatient and interscan variability in coronary artery calcium (CAC) studies.
  
  
  METHODS
  We scanned 144 patients twice with or without the calibration phantom and then scanned 93 patients with a single calcific lesion twice and, finally, scanned a cork heart with calcific foci.
  
  
  RESULTS
  There were no linear correlations in computed tomography Hounsfield unit (CT HU) and CT HU interscan variation between blood pool and phantom plugs at any slice level in patient groups (p > 0.05). The CT HU interscan variation in phantom plugs (2.11 HU) was less than that of the blood pool (3.47 HU; p < 0.05) and CAC lesion (20.39; p < 0.001). Comparing images with and without a calibration phantom, there was a significant decrease in CT HU as well as an increase in noise and peak values in patient studies and the cork phantom study.
  
  
  CONCLUSIONS
  The CT HU attenuation variations of the interpatient and interscan blood pool, calibration phantom plug, and cork coronary arteries were not parallel. Therefore, the ability to adjust the CT HU variation of calcific lesions by a calibration phantom is problematic and may worsen the problem.
authors.affiliation: Department of Medicine, Division of Cardiology, Harbor-UCLA Research and Education Institute, 1124 W. Carson Street RB-2, Torrance, CA 90502, USA. budoff@flash.net
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Budoff
authors.forename: Songshou
authors.initials: S
authors.lastname: Mao
authors.forename: Bin
authors.initials: B
authors.lastname: Lu
authors.forename: Junichiro
authors.initials: J
authors.lastname: Takasu
authors.forename: Janis
authors.initials: J
authors.lastname: Child
authors.forename: Sivi
authors.initials: S
authors.lastname: Carson
authors.forename: Hans
authors.initials: H
authors.lastname: Fisher
mesh_terms: D016477:Artifacts; D002114:Calcinosis / Q000000981:diagnostic imaging; D002118:Calcium / Q000032:analysis*; D002138:Calibration; D009202:Cardiomyopathies / Q000000981:diagnostic imaging*; D003331:Coronary Vessels / Q000737:chemistry*; D006801:Humans; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000592:standards
chemical_list: D002118:Calcium