title: Quantitative assessment of inter-observer variability in target volume delineation on stereotactic radiotherapy treatment for pituitary adenoma and meningioma near optic tract.
abstract: BACKGROUND
  To assess inter-observer variability in delineating target volume and organs at risk in benign tumor adjacent to optic tract as a quality assurance exercise.
  
  
  METHODS
  We quantitatively analyzed 21 plans made by 11 clinicians in seven CyberKnife centers. The clinicians were provided with a raw data set (pituitary adenoma and meningioma) including clinical information, and were asked to delineate the lesions and create a treatment plan. Their contouring and plans (10 adenoma and 11 meningioma plans), were then compared. In addition, we estimated the influence of differences in contouring by superimposing the respective contours onto a default plan.
  
  
  RESULTS
  The median planning target volume (PTV) and the ratio of the largest to the smallest contoured volume were 9.22 cm3 (range, 7.17-14.3 cm3) and 1.99 for pituitary adenoma, and 6.86 cm3 (range 6.05-14.6 cm3) and 2.41 for meningioma. PTV volume was 10.1±1.74 cm3 for group 1 with a margin of 1-2 mm around the CTV (n=3) and 9.28±1.8 cm3 (p=0.51) for group 2 with no margin (n=7) in pituitary adenoma. In meningioma, group 1 showed larger PTV volume (10.1±3.26 cm3) than group 2 (6.91±0.7 cm3, p=0.03). All submitted plan keep the irradiated dose to optic tract within the range of 50 Gy (equivalent total doses in 2 Gy fractionation). However, contours superimposed onto the dose distribution of the default plan indicated that an excessive dose 23.64 Gy (up to 268% of the default plan) in pituitary adenoma and 24.84 Gy (131% of the default plan) in meningioma to the optic nerve in the contours from different contouring.
  
  
  CONCLUSIONS
  Quality assurance revealed inter-observer variability in contour delineation and their influences on planning for pituitary adenoma and meningioma near optic tract.
authors.affiliation: Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajiicho Kawaramachi Hirokoji, Kamigyo-ku, Kyoto 602-8566 Japan. hideya10@hotmail.com
authors.forename: Hideya
authors.initials: H
authors.lastname: Yamazaki
authors.forename: Hiroya
authors.initials: H
authors.lastname: Shiomi
authors.forename: Takuji
authors.initials: T
authors.lastname: Tsubokura
authors.forename: Naohiro
authors.initials: N
authors.lastname: Kodani
authors.forename: Takuya
authors.initials: T
authors.lastname: Nishimura
authors.forename: Norihiro
authors.initials: N
authors.lastname: Aibe
authors.forename: Hiroki
authors.initials: H
authors.lastname: Udono
authors.forename: Manabu
authors.initials: M
authors.lastname: Nishikata
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Baba
authors.forename: Mikio
authors.initials: M
authors.lastname: Ogita
authors.forename: Koichi
authors.initials: K
authors.lastname: Yamashita
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Kotsuma
mesh_terms: D000236:Adenoma / Q000473:pathology / Q000601:surgery*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000592:standards; D008297:Male; D008579:Meningioma / Q000601:surgery*; D008875:Middle Aged; D015588:Observer Variation; D009929:Organ Size; D058958:Organs at Risk / Q000473:pathology; D010911:Pituitary Neoplasms / Q000473:pathology / Q000601:surgery*; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000706:statistics & numerical data*; D047368:Tumor Burden; D014795:Visual Pathways / Q000473:pathology