title: Scanner conformity in CT densitometry of the lungs.
abstract: OBJECTIVE
  To quantify inter- and intrascanner conformity in computed tomographic (CT) densitometry of the lungs.
  
  
  METHODS
  With six scanners from four manufacturers, a lung densitometry protocol with several variations was applied for performance comparison. Phantoms included water, air, and a humanoid thorax phantom equipped with a dog lung and exchangeable pseudolungs of polyethylene foam.
  
  
  RESULTS
  All scanners produced acceptable CT numbers (Hounsfield units) for water, but some not for air. An incorrect calibration of air density affected all CT numbers at lung densities, but the error was easily correctable. Some systems were more sensitive to object size than others were. Sensitivity of CT numbers to section thickness, reconstruction filter, zoom factor, and table height was small, except for two scanners in relation to section thickness.
  
  
  CONCLUSIONS
  After correction for poor air calibration, scanner conformity was acceptable when the reproducibility of lung densitometry in clinical practice was set as a reference.
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000000981:diagnostic imaging; D000388:Air; D000818:Animals; D002138:Calibration; D004285:Dogs; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000000981:diagnostic imaging*; D008953:Models, Anatomic; D008961:Models, Structural; D009765:Obesity / Q000000981:diagnostic imaging; D011095:Polyethylenes; D011856:Radiographic Image Enhancement; D013902:Radiography, Thoracic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D015898:Tomography Scanners, X-Ray Computed / Q000706:statistics & numerical data; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data; D014867:Water
chemical_list: D011095:Polyethylenes; D014867:Water