title: Quantifying and reducing the effect of calibration error on variability of PET/CT standardized uptake value measurements.
abstract: The purpose of this study was to measure the errors introduced by regular calibration of PET/CT scanners and to minimize the effect of calibration error on standardized uptake value measurements.
  
  
  METHODS
  Global calibration factors from 2 PET/CT scanners were recorded for 3.5 and 1.8 y, comparing manufacturer-recommended protocols with modified protocols to evaluate error contributions due to operator-influenced procedures. Dose calibrator measurements were evaluated using National Institute of Standards and Technology-traceable sources.
  
  
  RESULTS
  Dose calibrator variability was less than 1%, although there was a consistent bias. Global scaling variability was reduced from 6% to 4% for scanner 1 and from 11% to 4% for scanner 2 when quality assurance and quality control procedures were applied to the calibration protocol. When calibrations were done using a (68)Ge/(68)Ga phantom, the variability for both scanners was reduced to approximately 3%.
  
  
  CONCLUSIONS
  Applying quality assurance and quality control procedures to scanner calibration reduces variability, but there is a still a residual longitudinal scanner variability of 3%-4%. The procedures proposed here reduce the impact of operator error on scanner calibration and thereby minimize longitudinal variability in standardized uptake value measurements.
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Lockhart
authors.forename: Lawrence R
authors.initials: LR
authors.lastname: MacDonald
authors.forename: Adam M
authors.initials: AM
authors.lastname: Alessio
authors.forename: Wendy A
authors.initials: WA
authors.lastname: McDougald
authors.forename: Robert K
authors.initials: RK
authors.lastname: Doot
authors.forename: Paul E
authors.initials: PE
authors.lastname: Kinahan
mesh_terms: D000465:Algorithms; D002138:Calibration; D002588:Cesium Radioisotopes / Q000592:standards; D005462:Fluorine Radioisotopes / Q000592:standards; D005710:Gallium Radioisotopes / Q000592:standards; D005857:Germanium / Q000592:standards; D007091:Image Processing, Computer-Assisted; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000592:standards*; D011868:Radioisotopes / Q000592:standards; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012015:Reference Standards; D015203:Reproducibility of Results; D014055:Tomography, Emission-Computed / Q000592:standards*
chemical_list: D002588:Cesium Radioisotopes; D005462:Fluorine Radioisotopes; D005710:Gallium Radioisotopes; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D005857:Germanium