Inter-observer variation of hippocampus delineation in hippocampal avoidance prophylactic cranial irradiation

© 2018, Federación de Sociedades Españolas de Oncología (FESEO). Background: Hippocampal avoidance prophylactic cranial irradiation (HA-PCI) techniques have been developed to reduce radiation damage to the hippocampus. An inter-observer hippocampus delineation analysis was performed and the influence of the delineation variability on dose to the hippocampus was studied. Materials and methods: For five patients, seven observers delineated both hippocampi on brain MRI. The intra-class correlation (ICC) with absolute agreement and the generalized conformity index (CI gen ) were computed. Median surfaces over all observers’ delineations were created for each patient and regional outlining differences were analysed. HA-PCI dose plans were made from the median surfaces and we investigated whether dose constraints in the hippocampus could be met for all delineations. Results: The ICC for the left and right hippocampus was 0.56 and 0.69, respectively, while the CI gen ranged from 0.55 to 0.70. The posterior and anterior-medial hippocampal regions had most variation with SDs ranging from approximately 1 to 2.5 mm. The mean dose (D mean ) constraint was met for all delineations, but for the dose received by 1% of the hippocampal volume (D 1% ) violations were observed. Conclusion: The relatively low ICC and CI gen indicate that delineation variability among observers for both left and right hippocampus was large. The posterior and anterior-medial border have the largest delineation inaccuracy. The hippocampus D mean constraint was not violated.

Jaar van publicatie:2019