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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Vet. Sci. | doi: 10.3389/fvets.2019.00345

In vivo diffusion tensor magnetic resonance tractography of the sheep brain: an atlas of the ovine white matter fiber bundles

  • 1Other, Italy
  • 2Vita-Salute San Raffaele University, Italy
  • 3San Raffaele Scientific Institute (IRCCS), Italy
  • 4Department of Health, Animal Science and Food Safety, Faculty of Veterinary Medicine, University of Milan, Italy
  • 5Philips (Italy), Italy
  • 6Department of Veterinary Medicine, Faculty of Veterinary Medicine, University of Milan, Italy
  • 7Other, Italy
  • 8Department of Medical Biotechnology and Translational Medicine, Faculty of Medicine and Surgery, University of Milan, Italy
  • 9Humanitas Clinical and Research Center, Milan University, Italy
  • 10Humanitas Research Hospital, Italy
  • 11Department of Oncology and Hematology Oncology, Faculty of Medicine and Surgery, University of Milan, Italy

Diffusion Tensor Magnetic Resonance Imaging (DTI) allows to decode the mobility of water molecules in cerebral tissue, which is highly directional along myelinated fibers. By integrating the direction of highest water diffusion through the tissue, DTI Tractography enables a non-invasive dissection of brain fiber bundles. As such, this technique is a unique probe for in vivo characterization of white matter architecture. Unravelling the principal brain texture features of preclinical models that are advantageously exploited in experimental neuroscience is crucial to correctly evaluate investigational findings and to correlate them with real clinical scenarios. Although structurally similar to the human brain, the gyrencephalic ovine model has not yet been characterized by a systematic DTI study. Here we present the first in vivo sheep (ovis aries) tractography atlas, where the course of the main white matter fiber bundles of the ovine brain has been reconstructed. In the context of the EU’s Horizon EDEN2020 project, in vivo brain MRI protocol for ovine animal models was optimized on a 1.5T scanner. High resolution conventional MRI scans and DTI sequences (b-value=1000 s/mm2, 15 directions) were acquired on ten anesthetized sheep ovis aries, in order to define the diffusion features of normal adult ovine brain tissue. Topography of the ovine cortex was studied and DTI maps were derived, to perform DTI tractography reconstruction of the corticospinal tract, corpus callosum, fornix, visual pathway and occipitofrontal fascicle, bilaterally for all the animals. Binary masks of the tracts were then coregistered and reported in the space of a standard stereotaxic ovine reference system, to demonstrate the consistency of the fiber bundles and the minimal inter-subject variability in a unique tractography atlas.
Our results determine the feasibility of a protocol to perform in vivo DTI tractography of the sheep, providing a reliable reconstruction and 3D rendering of major ovine fiber tracts underlying different neurological functions. Estimation of fiber directions and interactions would lead to a more comprehensive understanding of the sheep’s brain anatomy, potentially exploitable in preclinical experiments, thus representing a precious tool for veterinaries and researchers.

Keywords: Diffusion Tensor Imaging, DTI tractography, Sheep, Brain, Atlas

Received: 25 Jul 2019; Accepted: 24 Sep 2019.

Copyright: © 2019 Pieri, Trovatelli, Cadioli, Zani, Brizzola, Ravasio, Acocella, Di Giancamillo, Malfassi, Dolera, Riva, Bello, Falini and Castellano. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: MD, PhD. Antonella Castellano, Other, Milan, Lombardy, Italy, castellano.antonella@hsr.it