title: Multi-centre calibration of an adaptive thresholding method for PET-based delineation of tumour volumes in radiotherapy planning of lung cancer.
abstract: OBJECTIVE
  To evaluate the calibration of an adaptive thresholding algorithm (contrast-oriented algorithm) for FDG PET-based delineation of tumour volumes in eleven centres with respect to scanner types and image data processing by phantom measurements.
  
  
  METHODS
  A cylindrical phantom with spheres of different diameters was filled with FDG realizing different signal-to-background ratios and scanned using 5 Siemens Biograph PET/CT scanners, 5 Philips Gemini PET/CT scanners, and one Siemens ECAT-ART PET scanner. All scans were analysed by the contrast-oriented algorithm implemented in two different software packages. For each site, the threshold SUVs of all spheres best matching the known sphere volumes were determined. Calibration parameters a and b were calculated for each combination of scanner and image-analysis software package. In addition, "scanner-type-specific" calibration curves were determined from all values obtained for each combination of scanner type and software package. Both kinds of calibration curves were used for volume delineation of the spheres.
  
  
  RESULTS
  Only minor differences in calibration parameters were observed for scanners of the same type (Δa ≤4%, Δb ≤14%) provided that identical imaging protocols were used whereas significant differences were found comparing calibration parameters of the ART scanner with those of scanners of different type (Δa ≤60%, Δb ≤54%). After calibration, for all scanners investigated the calculated SUV thresholds for auto-contouring did not differ significantly (all p>0.58). The resulting sphere volumes deviated by less than -7% to +8% from the true values.
  
  
  CONCLUSIONS
  After multi-centre calibration the use of the contrast-oriented algorithm for FDG PET-based delineation of tumour volumes in the different centres using different scanner types and specific imaging protocols is feasible.
authors.affiliation: Department of Nuclear Medicine, Saarland University Medical Center, 66421 Homburg, Germany. andrea.schaefer@uks.eu
authors.forename: A
authors.initials: A
authors.lastname: Schaefer
authors.forename: U
authors.initials: U
authors.lastname: Nestle
authors.forename: S
authors.initials: S
authors.lastname: Kremp
authors.forename: D
authors.initials: D
authors.lastname: Hellwig
authors.forename: A
authors.initials: A
authors.lastname: Grgic
authors.forename: H G
authors.initials: HG
authors.lastname: Buchholz
authors.forename: W
authors.initials: W
authors.lastname: Mischke
authors.forename: C
authors.initials: C
authors.lastname: Gromoll
authors.forename: P
authors.initials: P
authors.lastname: Dennert
authors.forename: M
authors.initials: M
authors.lastname: Plotkin
authors.forename: S
authors.initials: S
authors.lastname: Senftleben
authors.forename: D
authors.initials: D
authors.lastname: Thorwarth
authors.forename: M
authors.initials: M
authors.lastname: Tosch
authors.forename: A
authors.initials: A
authors.lastname: Wahl
authors.forename: H
authors.initials: H
authors.lastname: Wengenmair
authors.forename: C
authors.initials: C
authors.lastname: Rübe
authors.forename: C-M
authors.initials: CM
authors.lastname: Kirsch
mesh_terms: D000465:Algorithms; D002138:Calibration; D019544:Equipment Failure Analysis / Q000592:standards; D005858:Germany; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000592:standards*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000592:standards*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity