Cranial organs at risk delineation: heterogenous practices in radiotherapy planning

Guillaume Vogin*, Liza Hettal, Clarisse Bartau, Juliette Thariat, Marie Virginie Claeys, Guillaume Peyraga, Paul Retif, Ulrike Schick, Delphine Antoni, Zsuzsa Bodgal, Frederic Dhermain, Loic Feuvret

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

9 Citations (Scopus)


Background: Segmentation is a crucial step in treatment planning that directly impacts dose distribution and optimization. The aim of this study was to evaluate the inter-individual variability of common cranial organs at risk (OAR) delineation in neurooncology practice. Methods: Anonymized simulation contrast-enhanced CT and MR scans of one patient with a solitary brain metastasis was used for delineation and analysis. Expert professionals from 16 radiotherapy centers involved in brain structures delineation were asked to segment 9 OAR on their own treatment planning system. As reference, two experts in neurooncology, produced a unique consensual contour set according to guidelines. Overlap ratio, Kappa index (KI), volumetric ratio, Commonly Contoured Volume, Supplementary Contoured Volume were evaluated using Artiview™ v 2.8.2—according to occupation, seniority and level of expertise of all participants. Results: For the most frequently delineated and largest OAR, the mean KI are often good (0.8 for the parotid and the brainstem); however, for the smaller OAR, KI degrade (0.3 for the optic chiasm, 0.5% for the cochlea), with a significant discrimination (p < 0.01). The radiation oncologists, members of Association des Neuro-Oncologue d’Expression Française society performed better in all indicators compared to non-members (p < 0.01). Our exercise was effective in separating the different participating centers with 3 of the reported indicators (p < 0.01). Conclusion: Our study illustrates the heterogeneity in normal structures contouring between professionals. We emphasize the need for cerebral OAR delineation harmonization—that is a major determinant of therapeutic ratio and clinical trials evaluation.

Original languageEnglish
Article number26
JournalRadiation Oncology
Issue number1
Publication statusPublished - Dec 2021
Externally publishedYes


  • Continuing education
  • Inter individual variability
  • Neuroimaging
  • Radiotherapy
  • Segmentation


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