title: Inter-observer and intra-observer reliability for lung cancer target volume delineation in the 4D-CT era.
abstract: OBJECTIVE
  To investigate inter-observer and intra-observer target volume delineation (TVD) error in 4D-CT imaging of thoracic tumours.
  
  
  METHODS
  Primary and nodal gross tumour volumes (GTV) of 10 lung tumours on the 10 respiratory phases of a 4D-CT scan were contoured by six radiation oncologist observers. Inter-observer and intra-observer variability were assessed by the coefficient of variation (COV) and the volume overlap index (VOI). ANOVA was performed to assess differences in inter-observer and intra-observer variability based on patient case difficulty, respiratory phase, physician seniority, and physician observer.
  
  
  RESULTS
  VOI analysis determined that inter-observer was a more significant source of error than intra-observer variability. VOI improved with the use of 4D-CT as compared to conventional CT. ANOVA analysis for COVs found case difficulty (easy versus difficult) to be significant for inter-observer primary tumour and intra-observer nodal disease delineation. Physician seniority, respiratory phase, and individual physician were not found to be significant for TVD error.
  
  
  CONCLUSIONS
  Variability in TVD is a major source of error in 4D-CT treatment planning. Development of measures to reduce inter-observer and intra-observer TVD variability are necessary in order to deliver high quality radiotherapy.
authors.affiliation: Department of Radiation Oncology, London Regional Cancer Program, London, Ont., Canada.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Louie
authors.forename: George
authors.initials: G
authors.lastname: Rodrigues
authors.forename: Jason
authors.initials: J
authors.lastname: Olsthoorn
authors.forename: David
authors.initials: D
authors.lastname: Palma
authors.forename: Edward
authors.initials: E
authors.lastname: Yu
authors.forename: Brian
authors.initials: B
authors.lastname: Yaremko
authors.forename: Belal
authors.initials: B
authors.lastname: Ahmad
authors.forename: Inge
authors.initials: I
authors.lastname: Aivas
authors.forename: Stewart
authors.initials: S
authors.lastname: Gaede
mesh_terms: D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden