Abstract #3537

Axon diameter estimation in fixed human optic chiasm using diffusion weighted MR microscopy and microstructure-informed tractography

Mohammad Ashtarayeh¹, Tobias Streubel^1,2, Joao Periquito³, Andreas Pohlmann³, Thoralf Niendorf³, Evgeniya Kirilina^2,4, Markus Morawski⁵, Carsten Jäger², Stefan Geyer², Muhamed Barakovic⁶, Alessandro Daducci⁷, and Siawoosh Mohammadi¹

¹Department of Systems Neurosciences, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, ²Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ³Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck-Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, ⁴Neurocomputation and Neuroimaging Unit, Department of Education and Psychology, Freie Universität Berlin, Berlin, Germany, ⁵Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany, ⁶Signal Processing Lab (LTS5), Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland, ⁷Department of computer science, University of Verona, Verona, Italy

We estimated mean axon diameter of ipsilateral bundles in a fixed human optic chiasm sample using diffusion weighted MR microscopy and COMMIT framework. We computed that the resolution limit for axon diameters of our dMRI data is about 1.3 µm, indicating that our approach is sensitive to a larger range of axon diameter distribution (ADD) than in-vivo dMRI studies. We found a similar pattern in the estimated ADD using MRI as was reported by a histological analysis of macaque monkeys’ optic chiasm, indicating that the estimated ADD provides similar sensitivity to regional differences in microstructure properties as in ex-vivo histology.

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