1CMRR, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, 2Department of Physics, University of Sao Paulo, Ribeirao Preto, Brazil, 3Department of Medicine, University of Minnesota, Minneapolis, MN, United States, 4Division of Biostatistics, University of Minnesota, Minneapolis, MN, United States, 5Department of Medicine and Surgery, University of Salerno, Baronissi, Italy