1Molecular Imaging Center, Department of Biomedicine, University of Bergen, Bergen, Norway, 2Department of Radiology, Haukeland University Hospital, Bergen, Norway, 3Department of Physics, University of Bergen, Bergen, Norway, 4Department of Physics and Technology, University of Bergen, Bergen, Norway, 5Christian Michelsen Research, Bergen, Norway, 6MedViz Research Cluster, Bergen, Norway, 7KG Jebsen Centre for MS-Research, Department of Clinical Medicine, University of Bergen, Bergen, Norway, 8The Norwegian Multiple Sclerosis Competence Centre, Department of Neurology, Haukeland University Hospital, Bergen, Norway