Is the intra-axonal T2 relaxation time related to the axonal calibre? A diffusion-relaxation and histological data study
Muhamed Barakovic1,2,3,4, Marco Pizzolato4,5, Cristina Granziera1,2, Jean-Philippe Thiran4,6,7, Derek K. Jones3,8, and Erick Jorge Canales-Rodríguez4
1Translational Imaging in Neurology (ThINk) Basel, Department of Biomedical Engineering, University Hospital Basel and University of Basel, Basel, Switzerland, 2MS Center and Research Center for Clinical Neuroimmunology and Neuroscience Basel, University Hospital Basel and University of Basel, Basel, Switzerland, 3Cardiff University Brain Research Imaging Centre, Cardiff University, Cardiff, Wales, United Kingdom, 4Signal Processing Laboratory 5 (LTS5), École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 5Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kgs. Lyngby, Denmark, 6Radiology Department, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland, 7Centre d’Imagerie Biomédicale (CIBM), EPFL, Lausanne, Switzerland, 8Mary MacKillop Institute for Health Research, Faculty of Health Sciences, Australian Catholic University, Melbourne, Australia
The main limitation of current axon diameter mapping techniques is that the diffusion MRI (dMRI) signals from axons smaller than 2.0 μm are practically undistinguished from each other, even for the most advanced human scanners. Consequently, there is a resolution limit for the in vivo estimation of axon diameters from dMRI data. Therefore, it would be desirable to find another source of MRI contrast sensitive to the axonal calibre. This proof-of-concept study used a surface-based relaxation model to investigate whether the intra-axonal T2 estimated in a human brain is related to the inner axon radius measured from histological data.
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