The effect of dental artifacts, contrast media, and experience on interobserver contouring variations in head and neck anatomy.
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.
O'Daniel
Jennifer C
JC
Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Rosenthal
David I
DI
Garden
Adam S
AS
Barker
Jerry L
JL
Ahamad
Anesa
A
Ang
K Kian
KK
Asper
Joshua A
JA
Blanco
Angel I
AI
de Crevoisier
Renaud
R
Holsinger
F Christopher
FC
Patel
Chirag B
CB
Schwartz
David L
DL
Wang
He
H
Dong
Lei
L
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
D003287:Contrast Media