1. Department of Thoracic Surgery, Japan Red Cross Society Nagano Hospital , 5-22-1, Wakasato, Nagano, Nagano 380-8582 , Japan
2. Division of General Thoracic Surgery , Department of Surgery, , 3-1-1, Asahi, Matsumoto, Nagano , Japan
3. Shinshu University School of Medicine , Department of Surgery, , 3-1-1, Asahi, Matsumoto, Nagano , Japan