1University Medical Center Freiburg, Dept. of Radiology - Medical Physics, Freiburg, Germany, 2Beckman Institute, Dept. of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 3Heart Institute and Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, United States, 4University Medical Center Freiburg, Dept. of Neuroradiology - Freiburg Brain Imaging, Freiburg, Germany