Regional analysis of volumes and reproducibilities of automatic and manual hippocampal segmentations.
OBJECTIVE
Precise and reproducible hippocampus outlining is important to quantify hippocampal atrophy caused by neurodegenerative diseases and to spare the hippocampus in whole brain radiation therapy when performing prophylactic cranial irradiation or treating brain metastases. This study aimed to quantify systematic differences between methods by comparing regional volume and outline reproducibility of manual, FSL-FIRST and FreeSurfer hippocampus segmentations.


METHODS
This study used a dataset from ADNI (Alzheimer's Disease Neuroimaging Initiative), including 20 healthy controls, 40 patients with mild cognitive impairment (MCI), and 20 patients with Alzheimer's disease (AD). For each subject back-to-back (BTB) T1-weighted 3D MPRAGE images were acquired at time-point baseline (BL) and 12 months later (M12). Hippocampi segmentations of all methods were converted into triangulated meshes, regional volumes were extracted and regional Jaccard indices were computed between the hippocampi meshes of paired BTB scans to evaluate reproducibility. Regional volumes and Jaccard indices were modelled as a function of group (G), method (M), hemisphere (H), time-point (T), region (R) and interactions.


RESULTS
For the volume data the model selection procedure yielded the following significant main effects G, M, H, T and R and interaction effects G-R and M-R. The same model was found for the BTB scans. For all methods volumes reduces with the severity of disease. Significant fixed effects for the regional Jaccard index data were M, R and the interaction M-R. For all methods the middle region was most reproducible, independent of diagnostic group. FSL-FIRST was most and FreeSurfer least reproducible.


CONCLUSIONS
A novel method to perform detailed analysis of subtle differences in hippocampus segmentation is proposed. The method showed that hippocampal segmentation reproducibility was best for FSL-FIRST and worst for Freesurfer. We also found systematic regional differences in hippocampal segmentation between different methods reinforcing the need of adopting harmonized protocols.
Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands.
Fabian
http://orcid.org/0000-0002-5428-5131
F
Bartel
Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands.|Department of Radiology, VU University Medical Center, Amsterdam, The Netherlands.
Hugo
H
Vrenken
Department of Mathematics, VU University Amsterdam, Amsterdam, The Netherlands.
Fetsje
F
Bijma
Department of Radiology, VU University Medical Center, Amsterdam, The Netherlands.|Image Analysis Center, VU University Medical Center, Amsterdam, The Netherlands.
Frederik
F
Barkhof
Department of Radiotherapy Physics, University of Manchester, Manchester, United Kingdom.
Marcel
M
van Herk
Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands.
Jan C
JC
de Munck
D000544:Alzheimer Disease / Q000175:diagnosis* / Q000378:metabolism; D016208:Databases, Factual; D005260:Female; D006624:Hippocampus / Q000000981:diagnostic imaging* / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological