title: Intraobserver and interobserver variability in GTV delineation on FDG-PET-CT images of head and neck cancers.
abstract: OBJECTIVE
  To determine if the addition of fluorodeoxyglucose positron emission tomography (FDG-PET) data changes primary site gross tumor volumes (GTVs) in head and neck cancers.
  
  
  METHODS
  Computed tomography (CT), contrast-enhanced CT, and FDG-PET-CT scans were obtained in 10 patients with head and neck cancers. Eight experienced observers (6 head and neck oncologists and 2 neuro-radiologists) with access to clinical and radiologic reports outlined primary site GTVs on each modality. Three cases were recontoured twice to assess intraobserver variability. The magnitudes of the GTVs were compared. Intra- and interobserver variability was assessed by a two-way repeated measures analysis of variance. Inter- and intraobserver reliability were calculated.
  
  
  RESULTS
  There were no significant differences in the GTVs across the image modalities when compared as ensemble averages; the Wilcoxon matched-pairs signed-rank test showed that CT volumes were larger than PET-CT. Observers demonstrated the greatest consistency and were most interchangeable on contrast-enhanced CT; they performed less reliably on PET-CT.
  
  
  CONCLUSIONS
  The addition of PET-CT to primary site GTV delineation of head and neck cancers does not change the volume of the GTV defined by this group of expert observers in this patient sample. An FDG-PET may demonstrate differences in neck node delineation and in other disease sites.
authors: Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada. Stephen.Breen@rmp.uhn.on.ca
authors: Stephen L
authors: SL
authors: Breen
authors: Julia
authors: J
authors: Publicover
authors: Shiroma
authors: S
authors: De Silva
authors: Greg
authors: G
authors: Pond
authors: Kristy
authors: K
authors: Brock
authors: Brian
authors: B
authors: O'Sullivan
authors: Bernard
authors: B
authors: Cummings
authors: Laura
authors: L
authors: Dawson
authors: Anne
authors: A
authors: Keller
authors: John
authors: J
authors: Kim
authors: Jolie
authors: J
authors: Ringash
authors: Eugene
authors: E
authors: Yu
authors: Aaron
authors: A
authors: Hendler
authors: John
authors: J
authors: Waldron
mesh_terms: D005260:Female; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000175:diagnosis*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D015588:Observer Variation; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18