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J Neurol Surg B Skull Base 2018; 79(05): 475-481
DOI: 10.1055/s-0037-1618577
Original Article
Georg Thieme Verlag KG Stuttgart · New York

Three-Dimensional Volumetric Segmentation of Pituitary Tumors: Assessment of Inter-rater Agreement and Comparison with Conventional Geometric Equations

Karl Lindberg
1   Department of Neurosurgery, Sahlgrenska University Hospital, Gothenburg, Sweden
2   Department of Neuroradiology, Sahlgrenska University Hospital, Gothenburg, Sweden
,
Angelica Kouti
2   Department of Neuroradiology, Sahlgrenska University Hospital, Gothenburg, Sweden
,
Doerthe Ziegelitz
2   Department of Neuroradiology, Sahlgrenska University Hospital, Gothenburg, Sweden
,
Tobias Hallén
1   Department of Neurosurgery, Sahlgrenska University Hospital, Gothenburg, Sweden
,
Thomas Skoglund
1   Department of Neurosurgery, Sahlgrenska University Hospital, Gothenburg, Sweden
3   Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
,
Dan Farahmand
1   Department of Neurosurgery, Sahlgrenska University Hospital, Gothenburg, Sweden
3   Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
› Institutsangaben Funding None.
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Publikationsverlauf

22. August 2017

01. Dezember 2017

Publikationsdatum:
19. Januar 2018 (online)

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Abstract

Background The assessment of pituitary tumor (PT) volume is important in the treatment and follow-up of patients with PT. Previously, PT volume estimation has been performed by conventional geometric equations (CGE) such as abc/2 (simplified ellipsoid volume equation) and 4πr3/3 (sphere), both presuming a symmetric tumor shape, which occurs uncommonly in patients with PT. In contrast, three-dimensional (3D) voxel-based software segmentation takes the irregular and asymmetric shapes that PTs often possess into account and might be a more accurate method for PT volume segmentation.

The purpose of this study is twofold. (1) To compare 3D segmentation with CGE for PT volume estimation. (2) To assess inter-rater reliability in 3D segmentation of PTs.

Methods Nineteen high-resolution (1mm slice thickness) T1-weighted MRI examinations of patients with PT were independently analyzed and manually segmented, using the software ITK-SNAP, by two certified neuroradiologists. Concurrently, the volumes of the PTs were estimated with abc/2 and 4πr3/3 by a clinician, and the results were compared with the corresponding segmented volumes.

Results There was a significant decrease in PT volume attained from the segmentations compared with the calculations made with abc/2 (p < 0.001, mean volume 18% higher than segmentation) and 4πr3/3 (p < 0.001, mean volume 28% higher than segmentation). The intraclass correlation coefficient (ICC) for the two sets of segmented PTs was 0.99.

Conclusion CGE (abc/2 and 4πr3/3) significantly overestimates PT volume compared with 3D volumetric segmentation. The inter-rater agreement on manual 3D volumetric software segmentation is excellent.

Keywords

pituitary tumor volume - volumetric analysis - segmentation - abc/2

Ethical Approval

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.


The study was approved by the Regional Ethical Review Board in Gothenburg (No. 2015:100–15).


Informed Consent

Formal consent for this type of study is not required.