Inter-observer variability in the delineation of pharyngo-laryngeal tumor, parotid glands and cervical spinal cord: comparison between CT-scan and MRI.
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).
Geets
Xavier
X
Department of Radiation Oncology, Université Catholique de Louvain, St-Luc University Hospital, Brussels, Belgium.
Daisne
Jean-François
JF
Arcangeli
Stephano
S
Coche
Emmanuel
E
De Poel
Marian
M
Duprez
Thierry
T
Nardella
Grazia
G
Grégoire
Vincent
V
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