title: The effect of dental artifacts, contrast media, and experience on interobserver contouring variations in head and neck anatomy.
abstract: OBJECTIVE
  To investigate interobserver variability in the delineation of head-and-neck (H&N) anatomic structures on CT images, including the effects of image artifacts and observer experience.
  
  
  METHODS
  Nine observers (7 radiation oncologists, 1 surgeon, and 1 physician assistant) with varying levels of H&N delineation experience independently contoured H&N gross tumor volumes and critical structures on radiation therapy treatment planning CT images alongside reference diagnostic CT images for 4 patients with oropharynx cancer. Image artifacts from dental fillings partially obstructed 3 images. Differences in the structure volumes, center-of-volume positions, and boundary positions (1 SD) were measured. In-house software created three-dimensional overlap distributions, including all observers. The effects of dental artifacts and observer experience on contouring precision were investigated, and the need for contrast media was assessed.
  
  
  RESULTS
  In the absence of artifacts, all 9 participants achieved reasonable precision (1 SD < or =3 mm all boundaries). The structures obscured by dental image artifacts had larger variations when measured by the 3 metrics (1 SD = 8 mm cranial/caudal boundary). Experience improved the interobserver consistency of contouring for structures obscured by artifacts (1 SD = 2 mm cranial/caudal boundary).
  
  
  CONCLUSIONS
  Interobserver contouring variability for anatomic H&N structures, specifically oropharyngeal gross tumor volumes and parotid glands, was acceptable in the absence of artifacts. Dental artifacts increased the contouring variability, but experienced participants achieved reasonable precision even with artifacts present. With a staging contrast CT image as a reference, delineation on a noncontrast treatment planning CT image can achieve acceptable precision.
authors.affiliation: Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: O'Daniel
authors.forename: David I
authors.initials: DI
authors.lastname: Rosenthal
authors.forename: Adam S
authors.initials: AS
authors.lastname: Garden
authors.forename: Jerry L
authors.initials: JL
authors.lastname: Barker
authors.forename: Anesa
authors.initials: A
authors.lastname: Ahamad
authors.forename: K Kian
authors.initials: KK
authors.lastname: Ang
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Asper
authors.forename: Angel I
authors.initials: AI
authors.lastname: Blanco
authors.forename: Renaud
authors.initials: R
authors.lastname: de Crevoisier
authors.forename: F Christopher
authors.initials: FC
authors.lastname: Holsinger
authors.forename: Chirag B
authors.initials: CB
authors.lastname: Patel
authors.forename: David L
authors.initials: DL
authors.lastname: Schwartz
authors.forename: He
authors.initials: H
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Dong
mesh_terms: D016477:Artifacts; D003287:Contrast Media; D017266:Dental Prosthesis; D006257:Head / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D009333:Neck / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D015588:Observer Variation; D014066:Palatine Tonsil / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D010306:Parotid Gland / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed; D014067:Tonsillar Neoplasms / Q000000981:diagnostic imaging
chemical_list: D003287:Contrast Media