1Institute of Physics of Biological Systems, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, 2Department of Radiology, University Hospital Lausanne (CHUV), Lausanne, Switzerland, 3Department of Radiology, University of Lausanne (UNIL), Lausanne, Switzerland, 4Institute of Physics of Biological Systems, EPFL, Lausanne, Switzerland, 5Laboratory for Functional and Metabolic Imaging, EPFL, Lausanne, Switzerland, 6Department of Radiology, University of Geneva, Geneva, Switzerland