1. Department of Central Radiology, Kumamoto University Hospital, Chuo-ku, Kumamoto, Japan
2. Department of Diagnostic Radiology, Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
3. Department of Medical Physics, Faculty of Life Sciences, Chuo-ku, Kumamoto, Japan
4. Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kumamoto University, Chuo-ku, Kumamoto, Japan.