title: Inter-observer variability in the delineation of pharyngo-laryngeal tumor, parotid glands and cervical spinal cord: comparison between CT-scan and MRI.
abstract: OBJECTIVE
  The goal of this study was to compare the inter-observer variability between CT and MRI for the delineation of pharyngo-laryngeal SCC, parotid glands and spinal cord.
  
  
  METHODS
  Twenty pharyngo-laryngeal tumors were delineated by five observers on CT and MRI, using consistent delineation guidelines. Spinal cords and parotid glands were also delineated on CT and MRI by three observers. Mean GTVs and coefficients of variation were calculated for each observer and compared using ANOVA and its derived Pearson intra-class coefficient (R). For GTVs, a mismatch analysis (ratio between intersection and union volumes) was also performed.
  
  
  RESULTS
  Regarding oropharyngeal GTVs (n=10), no significant difference was observed between observers either with CT (33.9, 31.1, 32, 34 and 34.7 ml, five observers, P=0.47) or with MRI (30.5, 29.4, 30.1 and 31.5 ml, four observers, P=0.59). CVs (13.6 vs 12.9%), (0.98 vs 0.99) and mismatches (0.43 vs 0.42) between CT and MRI did not significantly differ. Regarding laryngeal-hypopharyngeal GTVs (n=10), no significant difference was observed between observers either on CT (18.1, 20.7, 20.9, 19.3 and 21.9 ml, five observers, P=0.29) or on MRI (19.3, 21.5, 20, 22.1 and 21.8 ml, five observers, P=0.16). CVs (20.2 vs 13.8%), (0.94 vs 0.94) and mismatches (0.31 vs 0.41) were comparable. Regarding OARs, a small but significant difference in mean parotid volume was observed between observers (P<0.001) and between modalities (P<0.001) (CT: 34.8, 29.4, and 26.8 ml; MRI: 30.6, 27.9 and 20.4 ml). Similar results were obtained for mean spinal cord volumes (CT: 10.7, 10.6, and 9.5 ml; MRI: 8.7, 8.5 and 8.2 ml; P=0.05).
authors.affiliation: Department of Radiation Oncology, Université Catholique de Louvain, St-Luc University Hospital, Brussels, Belgium.
authors.forename: Xavier
authors.initials: X
authors.lastname: Geets
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Daisne
authors.forename: Stephano
authors.initials: S
authors.lastname: Arcangeli
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Coche
authors.forename: Marian
authors.initials: M
authors.lastname: De Poel
authors.forename: Thierry
authors.initials: T
authors.lastname: Duprez
authors.forename: Grazia
authors.initials: G
authors.lastname: Nardella
authors.forename: Vincent
authors.initials: V
authors.lastname: Grégoire
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D019583:Dose Fractionation, Radiation; D006801:Humans; D007822:Laryngeal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D008279:Magnetic Resonance Imaging; D015588:Observer Variation; D010306:Parotid Gland / Q000000981:diagnostic imaging*; D010610:Pharyngeal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D011832:Radiation Injuries / Q000517:prevention & control; D012680:Sensitivity and Specificity; D013116:Spinal Cord / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed