1INM 4 - Medical Imaging Physics, Forschungszentrum Jülich, Jülich, Germany, 2Experimental Physics III, TU Dortmund University, Dortmund, Germany, 3Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany, 4German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany