Inter-observer variation of hippocampus delineation in hippocampal avoidance prophylactic cranial irradiation
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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 (CIgen) 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.
The ICC for the left and right hippocampus was 0.56 and 0.69, respectively, while the CIgen 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 (Dmean) constraint was met for all delineations, but for the dose received by 1% of the hippocampal volume (D1%) violations were observed.
The relatively low ICC and CIgen 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 Dmean constraint was not violated.
KeywordsSCLC HA-PCI Hippocampus delineation Inter-observer variation
The authors would like to thank C. Chun for her previous work and contribution to this study. This study was funded by ZonMW (Grand Number: 104002006), the Netherlands organisation for health research and development, the Dutch Cancer Society (KWF, Grand Number: 2013-6096) and Netherlands Cancer Institute (NKI) in Amsterdam. We would also like to acknowledge the government agency for Innovation by Science and Technology (A13/TT/1503—IWT/TBM) and NutsOhra (Project 100 3-105).
Compliance with ethical standards
Conflict of interest
All authors declare that they have no competing interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
For this analysis no formal consent is required.
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