title: In vivo mapping of human spinal cord microstructure at 300mT/m.
abstract: The ability to characterize white matter microstructure non-invasively has important applications for the diagnosis and follow-up of several neurological diseases. There exists a family of diffusion MRI techniques, such as AxCaliber, that provide indices of axon microstructure, such as axon diameter and density. However, to obtain accurate measurements of axons with small diameters (<5μm), these techniques require strong gradients, i.e. an order of magnitude higher than the 40-80mT/m currently available in clinical systems. In this study we acquired AxCaliber diffusion data at a variety of different q-values and diffusion times in the spinal cord of five healthy subjects using a 300mT/m whole body gradient system. Acquisition and processing were optimized using state-of-the-art methods (e.g., 64-channel coil, template-based analysis). Results consistently show an average axon diameter of 4.5+/-1.1μm in the spinal cord white matter. Diameters ranged from 3.0μm (gracilis) to 5.9μm (spinocerebellar tracts). Values were similar across laterality (left-right), but statistically different across spinal cord pathways (p<10(-5)). The observed trends are similar to those observed in animal histology. This study shows, for the first time, in vivo mapping of axon diameter in the spinal cord at 300mT/m, thus creating opportunities for applications in spinal cord diseases.
authors.affiliation: Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada.
authors.forename: Tanguy
authors.initials: T
authors.lastname: Duval
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, United States.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: McNab
authors.affiliation: A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States.
authors.forename: Kawin
authors.initials: K
authors.lastname: Setsompop
authors.affiliation: A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States.
authors.forename: Thomas
authors.initials: T
authors.lastname: Witzel
authors.affiliation: NMR Research Unit, Department of Neuroinflammation, Queen Square MS Centre, UCL Institute of Neurology, London, London, United Kingdom.
authors.forename: Torben
authors.initials: T
authors.lastname: Schneider
authors.affiliation: A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States.
authors.forename: Susie Yi
authors.initials: SY
authors.lastname: Huang
authors.affiliation: A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States.
authors.forename: Boris
authors.initials: B
authors.lastname: Keil
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Klawiter
authors.affiliation: A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States.
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Wald
authors.affiliation: Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada; Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montreal, QC, Canada. Electronic address: jcohen@polymtl.ca.
authors.forename: Julien
authors.initials: J
authors.lastname: Cohen-Adad
mesh_terms: D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D013116:Spinal Cord / Q000166:cytology*; D066127:White Matter / Q000166:cytology*
keywords: AxCaliber; Axon diameter; Diffusion MRI; Human; Quantification; Spinal cord