Francisco Javier Fritz1, Mohammad Ashtarayeh1, Joao Periquito2, Andreas Pohlmann2, Markus Morawski3, Carsten Jaeger4, Thoralf Niendorf2, Kerrin J. Pine4, Evgeniya Kirilina4,5, Nikolaus Weiskopf4,6, 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
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
R2*-angular dependency is modulated by fibre dispersion and the angular dependency is removed using high-order models. However, ex vivo experimental data results at small angular orientation and dispersion was only reflected in simulations when accounting for myelin-water contributions.
Figure 2: Experimental dataset: (A) GRE
MRI of the OC in all anatomical planes. Here the optic tracts (OT) and optical
nerves (ON) are indicated, together with the B0 direction (yellow
arrow). (B) The MR transversal images of the first three angular measurements
before (top row) and after coregistration (bottom row) (left). Using the
transformation matrix, the direction of B0 per angular measurement
were calculated (right).
Figure 5: Orientation dependence of the
parameters in M2 (β0M2 in the top row, β1M2
in the middle row and β2M2 in the bottom row) for the
simulated data without (A) and with myelin water (B) contribution, and
experimental (C) dataset. It is observed that the angular dependency is removed for β0M2
and β1M2 and transferred to β2M2 for
all dataset and fibre’s dispersions. Importantly,
the negative β2M2 values at small angles observed in the
experimental dataset are only replicated if the myelin pool is added to the
simulations.
