title: Quantification of FDG PET studies using standardised uptake values in multi-centre trials: effects of image reconstruction, resolution and ROI definition parameters.
abstract: OBJECTIVE
  Standardised uptake values (SUVs) depend on acquisition, reconstruction and region of interest (ROI) parameters. SUV quantification in multi-centre trials therefore requires standardisation of acquisition and analysis protocols. However, standardisation is difficult owing to the use of different scanners, image reconstruction and data analysis software. In this study we evaluated whether SUVs, obtained at three different institutes, may be directly compared after calibration and correction for inter-institute differences.
  
  
  METHODS
  First, an anthropomorphic thorax phantom containing variously sized spheres and activities, simulating tumours, was scanned and processed in each institute to evaluate differences in scanner calibration. Secondly, effects of image reconstruction and ROI method on recovery coefficients were studied. Next, SUVs were derived for tumours in 23 subjects. Of these 23 patients, four and ten were scanned in two institutes on an HR+ PET scanner and nine were scanned in one institute on an ECAT EXACT PET scanner. All phantom and clinical data were reconstructed using iterative reconstruction with various iterations, with both measured (MAC) and segmented attenuation correction (SAC) and at various image resolutions. Activity concentrations (AC) or SUVs were derived using various ROI isocontours.
  
  
  RESULTS
  Phantom data revealed differences in SUV quantification of up to 30%. After application-specific calibration, recovery coefficients obtained in each institute were equal to within 15%. Varying the ROI isocontour value resulted in a predictable change in SUV (or AC) for both phantom and clinical data. Variation of image resolution resulted in a predictable change in SUV quantification for large spheres/tumours (>5 cc) only. For smaller tumours (<2 cc), differences of up to 40% were found between high (7 mm) and low (10 mm) resolution images. Similar differences occurred when data were reconstructed with a small number of iterations. Finally, no significant differences between MAC and SAC reconstructed data were observed, except for tumours near the diaphragm.
  
  
  CONCLUSIONS
  Standardisation of acquisition, reconstruction and ROI methods is preferred for SUV quantification in multi-centre trials. Small unavoidable differences in methodology can be accommodated by performing a phantom study to assess inter-institute correction factors.
authors.affiliation: Department of Surgery, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Marinke
authors.initials: M
authors.lastname: Westerterp
authors.forename: Jan
authors.initials: J
authors.lastname: Pruim
authors.forename: Wim
authors.initials: W
authors.lastname: Oyen
authors.forename: Otto
authors.initials: O
authors.lastname: Hoekstra
authors.forename: Anne
authors.initials: A
authors.lastname: Paans
authors.forename: Eric
authors.initials: E
authors.lastname: Visser
authors.forename: Jan
authors.initials: J
authors.lastname: van Lanschot
authors.forename: Gerrit
authors.initials: G
authors.lastname: Sloof
authors.forename: Ronald
authors.initials: R
authors.lastname: Boellaard
mesh_terms: D000465:Algorithms; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007089:Image Enhancement / Q000379:methods / Q000592:standards*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods / Q000592:standards*; D015337:Multicenter Studies as Topic / Q000592:standards*; D009426:Netherlands; D049268:Positron-Emission Tomography / Q000592:standards*; D019275:Radiopharmaceuticals; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18