1. Department of Cardiovascular Medicine, Faculty of Medicine and Graduate School of Medicine Hokkaido University Kita 15, Nishi 7, Kita‐ku Sapporo Hokkaido 060‐8638 Japan
2. Department of Diagnostic Imaging, Faculty of Medicine and Graduate School of Medicine Hokkaido University Sapporo Japan
3. Department of Respiratory Medicine, Faculty of Medicine and Graduate School of Medicine Hokkaido University Sapporo Japan