title: Variability of gross tumor volume delineation in head-and-neck cancer using CT and PET/CT fusion.
abstract: OBJECTIVE
  To assess the need for gross tumor volume (GTV) delineation protocols in head-and-neck cancer (HNC) treatment planning by use of positron emission tomography (PET)/computed tomography (CT) fusion imaging. Assessment will consist of interobserver and intermodality variation analysis.
  
  
  METHODS
  Sixteen HNC patients were accrued for the study. Four physicians (2 neuroradiologists and 2 radiation oncologists) contoured GTV on 16 patients. Physicians were asked to contour GTV on the basis of the CT alone, and then on PET/CT fusion. Statistical analysis included analysis of variance for interobserver variability and Student's paired sample t test for intermodality and interdisciplinary variability. A Boolean pairwise analysis was included to measure degree of overlap.
  
  
  RESULTS
  Near-significant variation occurred across physicians' CT volumes (p = 0.09) and significant variation occurred across physicians' PET/CT volumes (p = 0.0002). The Boolean comparison correlates with statistical findings. One radiation oncologist's PET/CT fusion volumes were significantly larger than his CT volumes (p < 0.01). Conversely, the other radiation oncologist's CT volumes tended to be larger than his fusion volumes (p = 0.06). No significant interdisciplinary variation was seen. Significant disagreement occurred between radiation oncologists.
  
  
  CONCLUSIONS
  Significant differences in GTV delineation were found between multiple observers contouring on PET/CT fusion. The need for delineation protocol has been confirmed.
authors.affiliation: Department of Radiation Oncology, St. Vincent's Comprehensive Cancer Center, New York, NY, USA.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Riegel
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Berson
authors.forename: Sylvie
authors.initials: S
authors.lastname: Destian
authors.forename: Tracy
authors.initials: T
authors.lastname: Ng
authors.forename: Lawrence B
authors.initials: LB
authors.lastname: Tena
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Mitnick
authors.forename: Ping S
authors.initials: PS
authors.lastname: Wong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18