Abstract #2179

Improving in-vivo myelin and iron mapping from relaxation rates maps by incorporating relaxation rate changes from in-vivo to ex-vivo conditions

Francisco J Fritz¹, Tobias Streubel¹, Laurin Mordhorst¹, Herbert Mushumba², Klaus Püschel², Maria Morozova³, Markus Morawski^3,4, Carsten Jäger^3,4, Evgeniya Kirilina³, Nikolaus Weiskopf^3,5,6, and Siawoosh Mohammadi^1,3,7

¹Institut für Systemischeneurowissenschaften, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany, ²Rechtsmedizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany, ³Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ⁴Paul Flechsig Institute – Center for Neuropathology and Brain Research, University of Leipzig, Leipzig, Germany, ⁵Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, University of Leipzig, Leipzig, Germany, ⁶Wellcome Centre for Human Neuroimaging, Institute of Neurology, University College London, London, United Kingdom, ⁷Max Planck Research Group MR Physics, Max Planck Institute for Human Development, Berlin, Germany

Synopsis

Keywords: Relaxometry, Validation, Histology, Myelin, Iron, In vivo vs ex vivo, Fixation

Motivation: Estimating myelin and iron concentration maps from in-vivo MRI yields biased estimates because MR-to-microstructure linear mappings are derived from fixed-postmortem human brain tissue.

Goal(s): We assessed whether taking into account the changes of relaxation rates from in-vivo to hydrated fixed ex-vivo specimens would allow the use of current MR-to-microstructure linear mappings for in-vivo MRI.

Approach: We introduced a pipeline that accounts for the major relaxation-rate changes during fixation and hydration, and compared the estimated MRI-based myelin parameters to their counterparts from light microscopy in the human corpus callosum.

Results: We found that including these changes significantly improved the accuracy of the myelin estimates.

Impact: We proposed a new method that significantly improves the MRI-based myelin and iron maps estimation from in-vivo longitudinal and effective transverse relaxation rates.

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