Post-mortem human spinal cord microstructure at ultra-high field: toward a white matter bundle atlas
Poster No:
1792
Submission Type:
Abstract Submission
Authors:
Eléa GRANIER1, Raphaël Ly2, Frédéric Andersson3, Aymeric Amelot2, Christophe Destrieux4,2, Cyril Poupon1, Ivy Uszynski1
Institutions:
1BAOBAB, NeuroSpin, Université Paris-Saclay, CNRS, CEA, Gif-sur-Yvette, France, 2CHRU de Tours, Tours, France, 3UMR 1253, iBrain, Université de Tours, Inserm, Tours, France, 4UMR 1253, iBrain, Université de Tours, Inserm, Tours, france
First Author:
Co-Author(s):
Christophe Destrieux
UMR 1253, iBrain, Université de Tours, Inserm|CHRU de Tours
Tours, france|Tours, France
UMR 1253, iBrain, Université de Tours, Inserm|CHRU de Tours
Tours, france|Tours, France
Introduction:
Spinal cord injuries (SCI) strongly invalidate and significantly decrease patients' quality of life. A thorough study of spinal cord (SC) anatomy is required to understand these pathologies better2. Although SC studies have bloomed over the years, with extensive works led on rats and cats, the human spinal cord anatomy remains an object of interrogation because of the MRI constraints of in-vivo acquisitions as well as the difficulties of obtaining, extracting, and manipulating post-mortem samples. A consensus is still to be reached, as reviews suggest9, about axon diameters, fiber densities, and microstructural properties of the white matter (WM).
In this work, we present a characterization of the microstructure of a post-mortem spinal cord sample acquired on an ultra-high field 11.7T Bruker MRI system, paving the way toward an atlas of the white matter fiber bundles of a whole spinal cord
In this work, we present a characterization of the microstructure of a post-mortem spinal cord sample acquired on an ultra-high field 11.7T Bruker MRI system, paving the way toward an atlas of the white matter fiber bundles of a whole spinal cord
Methods:
A 5cm cervical sample (SC02152, fig.1) of a post-mortem human spinal cord was prepared by the iBrain Unit (University of Tours, France) before undergoing a two-session diffusion MRI protocol on an 11.7T Bruker MRI system involving (1) a hybrid diffusion MRI1 (HYDI) and (2) an AxCaliber3 protocols.
HYDI protocol: A 200μm isotropic resolution multiple-shell PGSE SE-EPI sequence (b=1500, 4500, 8000 s/mm2) was acquired along 25/60/90 diffusion directions, as well as a 150μm isotropic resolution anatomical T2-weighted scan, requiring up to 85 hours of scan time. The acquired data was fed to a Ginkgo Toolbox analysis pipeline composed of denoising and mask computation steps, followed by a diffusion tensor imaging4 (DTI) model giving quantitative fractional anisotropy (FA) and mean diffusivity (MD) maps as well as an analytical q-ball5 (aQBI) model to obtain a diffusion Orientation Distribution Functions (ODF) map which was used to perform regularized deterministic streamline tractography7 (8 seeds/voxel over the whole propagation domain, forward step=30μm, aperture angle=7.0°).
AxCaliber protocol: The AxCaliber protocol involved a single diffusion direction perpendicular to the axon fibers and included diffusion weighting with various diffusion durations (∆=16, 30, 60, 100, 150 ms) and gradient strengths (15 values between 20 and 300 mT/m) for a fixed diffusion plateau duration (δ=4ms), 100μm in-plane resolution, slice thickness TH=1mm, acquisition time 86h. After denoising and the computation of a thorough mask of the spinal cord, a fit of the signal decay was performed using the Ginkgo Toolbox with fixed parameters8 of 0.8*10-⁹m²/s for hindered diffusivity, 0.58*10-⁹m²/s for transverse intracellular diffusivity and 1.58*10-⁹m²/s for longitudinal intracellular diffusivity.
HYDI protocol: A 200μm isotropic resolution multiple-shell PGSE SE-EPI sequence (b=1500, 4500, 8000 s/mm2) was acquired along 25/60/90 diffusion directions, as well as a 150μm isotropic resolution anatomical T2-weighted scan, requiring up to 85 hours of scan time. The acquired data was fed to a Ginkgo Toolbox analysis pipeline composed of denoising and mask computation steps, followed by a diffusion tensor imaging4 (DTI) model giving quantitative fractional anisotropy (FA) and mean diffusivity (MD) maps as well as an analytical q-ball5 (aQBI) model to obtain a diffusion Orientation Distribution Functions (ODF) map which was used to perform regularized deterministic streamline tractography7 (8 seeds/voxel over the whole propagation domain, forward step=30μm, aperture angle=7.0°).
AxCaliber protocol: The AxCaliber protocol involved a single diffusion direction perpendicular to the axon fibers and included diffusion weighting with various diffusion durations (∆=16, 30, 60, 100, 150 ms) and gradient strengths (15 values between 20 and 300 mT/m) for a fixed diffusion plateau duration (δ=4ms), 100μm in-plane resolution, slice thickness TH=1mm, acquisition time 86h. After denoising and the computation of a thorough mask of the spinal cord, a fit of the signal decay was performed using the Ginkgo Toolbox with fixed parameters8 of 0.8*10-⁹m²/s for hindered diffusivity, 0.58*10-⁹m²/s for transverse intracellular diffusivity and 1.58*10-⁹m²/s for longitudinal intracellular diffusivity.
Results:
Fig. 1 displays the T2w image, the fractional anisotropy of the SC sample, and the whole sample tractogram, showcasing the principal unidirectionality of the 5,028,804 white matter fibers that connect to the spinal nerve roots. The axon diameter distribution shows preliminary results with values ranging from 1.02 to 1.48μm.
·Fig.1: Anatomical scans of SC02152 and results for both protocols
Conclusions:
A further clustering step based on the axonal diameter map could allow a fine segmentation of the white matter pathways of the human spinal cord sharing similar diameter ranges. Future work will focus on applying the same protocol and analysis procedure on an entire 60cm long spinal cord, hereby paving the way toward a first mesoscopic depiction of the white matter fiber bundles of a post-mortem human spinal cord.
This work benefited from government funding (ESR/EquipEx PRESENCE ANR-21-ESRE-0006, BrainDeepPhenotyping ANR-22-PESN-0006, Evonectome ANR-23-CE37-0021) managed by the French National Research Agency.
Samples were obtained from the body donation program of Université de Tours. Participants gave their written consent before death for using their entire body for educational or research purposes involving the anatomy laboratory. The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed.
This work benefited from government funding (ESR/EquipEx PRESENCE ANR-21-ESRE-0006, BrainDeepPhenotyping ANR-22-PESN-0006, Evonectome ANR-23-CE37-0021) managed by the French National Research Agency.
Samples were obtained from the body donation program of Université de Tours. Participants gave their written consent before death for using their entire body for educational or research purposes involving the anatomy laboratory. The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed.
Modeling and Analysis Methods:
Connectivity (eg. functional, effective, structural)
Diffusion MRI Modeling and Analysis 2
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
White Matter Anatomy, Fiber Pathways and Connectivity 1
Novel Imaging Acquisition Methods:
Diffusion MRI
Keywords:
Acquisition
Data analysis
HIGH FIELD MR
Modeling
MRI
Spinal Cord
Tractography
WHITE MATTER IMAGING - DTI, HARDI, DSI, ETC
1|2Indicates the priority used for review
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