1CMRR, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, 2Central European Institute of Technology, Masaryk University, Brno, Czech Republic, 3Department of Medicine, University of Minnesota, Minneapolis, MN, United States, 4Department of Physics, University of Sao Paolo, Ribeirao Preto, Brazil, 5Division of Biostatistics, University of Minnesota, Minneapolis, MN, United States