Inter-observer and intra-observer reliability for lung cancer target volume delineation in the 4D-CT era.
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.
Louie
Alexander V
AV
Department of Radiation Oncology, London Regional Cancer Program, London, Ont., Canada.
Rodrigues
George
G
Olsthoorn
Jason
J
Palma
David
D
Yu
Edward
E
Yaremko
Brian
B
Ahmad
Belal
B
Aivas
Inge
I
Gaede
Stewart
S
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