title: Vertex-wise shape analysis of the hippocampus: disentangling positional differences from volume changes.
abstract: Hippocampal atrophy and developmental positional variants may co-occur in various neurological disorders. We propose a surface-based framework to analyze independently volume and positioning. After extracting the spherical harmonics combined with point distribution models (SPHARM-PDM) from manual labels, we computed displacement vectors between individual surfaces and the template. Then, we computed surface-based Jacobian determinants (SJD) from these vectors to localize volume changes. To analyze positional variants, we constructed a mean meridian axis (MEMAX), inheriting the shape-constrained point correspondences of SPHARM, on which we compute local curvatures and position vectors. We validated our method on synthetic shapes, and a large database of healthy subjects and patients with temporal lobe epilepsy. Our comprehensive analysis showed that in patients atrophy and positional changes co-occurred at the level of the posterior hippocampus. Indeed, in this region, while SPHARM-PDM showed mirrored deformations, SJD detected atrophy, and shape analysis of MEMAX unveiled medial positioning due to bending.
authors: Department of Neurology and McConnell Brain Imaging Center, Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada. khs001@bic.mni.mcgill.ca
authors: Hosung
authors: H
authors: Kim
authors: Tommaso
authors: T
authors: Mansi
authors: Andrea
authors: A
authors: Bernasconi
authors: Neda
authors: N
authors: Bernasconi
mesh_terms: D000328:Adult; D000465:Algorithms; D001284:Atrophy; D001931:Brain Mapping / Q000379:methods; D016022:Case-Control Studies; D016208:Databases, Factual; D004351:Drug Resistance; D004827:Epilepsy / Q000473:pathology*; D004833:Epilepsy, Temporal Lobe / Q000473:pathology; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008953:Models, Anatomic; D015233:Models, Statistical; D013499:Surface Properties