Abstract #3318

Effects of fibre dispersion and myelin content on R2*: simulations and post-mortem experiments

Francisco Javier Fritz¹, Mohammad Ashtarayeh¹, Joao Periquito², Andreas Pohlmann², Markus Morawski³, Carsten Jaeger⁴, Thoralf Niendorf², Kerrin J. Pine⁴, Evgeniya Kirilina^4,5, Nikolaus Weiskopf^4,6, and Siawoosh Mohammadi¹

¹Institut für Systemische Neurowissenschaften, Universitätklinikum Hamburg-Eppendorf, Hamburg, Germany, ²Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck-Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, ³Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany, ⁴Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ⁵Center for Cognitive Neuroscience Berlin, Free University Berlin, Berlin, Germany, ⁶5Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Leipzig, Germany

We studied the impact of fibre dispersion and myelin on the angle-dependent gradient-recalled echo signal decay in simulation and experimental data from post-mortem tissue. We compared the classical log-mono-exponential and quadratic time-dependent signal model (M2) derived from Wharton and Bowtell’s forward-model with and without myelin-water contribution. We found that R₂*-angular dependency was modulated by fibre dispersion and the R₂*-angular dependency is removed using M2. We also observed that the higher-order parameter estimated from experimental data at small angles and dispersion was only reflected in simulations when accounting for myelin-water contributions, indicating that this pool needs to be added into M2.

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