1Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, Kobe, Japan, 2Radiology, Kobe University Graduate School of Medicine, Kobe, Japan, 3Radiology, Hyogo Cancer Center, Akashi, Japan, 4Toshiba Medical Systems Corporation, Otawara, Japan, 5Toshiba Medical Research Institute USA, Vernon Hills, IL, United States, 6Center for Radiology and Radiation Oncology, Kobe University Hospital, Kobe, Japan