title: The delineation of target volumes for radiotherapy of lung cancer patients.
abstract: OBJECTIVE
  Differences in the delineation of the gross target volume (GTV) and planning target volume (PTV) in patients with non-small-cell lung cancer are considerable. The focus of this work is on the analysis of observer-related reasons while controlling for other variables.
  
  
  METHODS
  In three consecutive patients, eighteen physicians from fourteen different departments delineated the GTV and PTV in CT-slices using a detailed instruction for target delineation. Differences in the volumes, the delineated anatomic lymph node compartments and differences in every delineated pixel of the contoured volumes in the CT-slices (pixel-by-pixel-analysis) were evaluated for different groups: ten radiation oncologists from ten departments (ROs), four haematologic oncologists and chest physicians from four departments (HOs) and five radiation oncologists from one department (RO1D).
  
  
  RESULTS
  Agreement (overlap > or = 70% of the contoured pixels) for the GTV and PTV delineation was found in 16.3% and 23.7% (ROs), 30.4% and 38.6% (HOs) and 32.8% and 35.9% (RO1D), respectively.
  
  
  CONCLUSIONS
  A large interobserver variability in the PTV and much more in the GTV delineation were observed in spite of a detailed instruction for delineation. The variability was smallest for group ROID where due to repeated discussions and uniform teaching a better agreement was achieved.
authors.affiliation: Department of Radiotherapy and Radiooncology, University Hospital Göttingen, Robert-Koch-Strasse, Germany. h.vorwerk@med.uni-goettingen.de
authors.forename: Hilke
authors.initials: H
authors.lastname: Vorwerk
authors.forename: Gabriele
authors.initials: G
authors.lastname: Beckmann
authors.forename: Michael
authors.initials: M
authors.lastname: Bremer
authors.forename: Maria
authors.initials: M
authors.lastname: Degen
authors.forename: Barbara
authors.initials: B
authors.lastname: Dietl
authors.forename: Rainer
authors.initials: R
authors.lastname: Fietkau
authors.forename: Tammo
authors.initials: T
authors.lastname: Gsänger
authors.forename: Robert Michael
authors.initials: RM
authors.lastname: Hermann
authors.forename: Markus Karl
authors.initials: MK
authors.lastname: Alfred Herrmann
authors.forename: Ulrike
authors.initials: U
authors.lastname: Höller
authors.forename: Michael
authors.initials: M
authors.lastname: van Kampen
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Körber
authors.forename: Burkhard
authors.initials: B
authors.lastname: Maier
authors.forename: Thomas
authors.initials: T
authors.lastname: Martin
authors.forename: Michael
authors.initials: M
authors.lastname: Metz
authors.forename: Ronald
authors.initials: R
authors.lastname: Richter
authors.forename: Birgit
authors.initials: B
authors.lastname: Siekmeyer
authors.forename: Martin
authors.initials: M
authors.lastname: Steder
authors.forename: Daniela
authors.initials: D
authors.lastname: Wagner
authors.forename: Clemens Friedrich
authors.initials: CF
authors.lastname: Hess
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Weiss
authors.forename: Hans
authors.initials: H
authors.lastname: Christiansen