title: Software upgrading in a CT scanner. Influence on quantitative CT.
abstract: OBJECTIVE
  In an attempt to improve field uniformity and CT number stability, the software in a CT scanner was replaced with a new version. The purpose of the present study was to investigate the influence of the software upgrading on density measurements.
  
  
  METHODS
  The upgrading influence was investigated by means of a torso phantom (European spinal). The phantom simulates a torso which contains 3 vertebrae of different densities.
  
  
  RESULTS
  Despite the use of a reference standard under the phantom, the software change resulted in: a) improved short-term precision; b) increased density values at 80 and 100 kVp, decreased at 130 kVp; and c) increased influence of the kVp on the values.
  
  
  CONCLUSIONS
  The results of the present study suggest that conversion factors have to be used in density values for reference populations as well as in the values of patients undergoing follow-up studies.
authors.affiliation: Medical Physics Department, Medical School, University of Ioannina, Greece.
authors.forename: J A
authors.initials: JA
authors.lastname: Kalef-Ezra
authors.forename: A H
authors.initials: AH
authors.lastname: Karantanas
mesh_terms: D015502:Absorptiometry, Photon; D006801:Humans; D019047:Phantoms, Imaging; D012984:Software; D013131:Spine / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods