1. Department of Cardiovascular and Thoracic Surgery; Hokkaido University Graduate School of Medicine; Sapporo Japan
2. Department of Cardiovascular and Thoracic Surgery, Faculty of Medicine; Hokkaido University; Sapporo Japan
3. Department of Radiology; Hokkaido University Hospital; Sapporo Japan
4. Department of Gastroenterology Surgery II, Faculty of Medicine; Hokkaido University; Sapporo Japan