1National Institute of Radiological Sciences, Chiba, Japan, 2Chiba University, Chiba, Japan, 3Department of Radiology, Kanagawa Children's Medical Center, Yokohama, Japan, 4Kanagawa Children's Medical Center, Yokohama, Japan, 5Siemens, Tokyo, Japan, 6Biomedical Imaging Technology Center, Burlington, MA, United States, 7University of Colorado, Cary, NC, United States