1 Department of Gastrointestinal and Hepato-Biliary-Pancreatic Surgery, Institute of Medicine, University of Tsukuba, Tsukuba, Japan.
2 Department of Radiology, Institute of Medicine, University of Tsukuba, Tsukuba, Japan; Advanced Imaging Center Tsukuba, Tsukuba, Japan.
3 Department of Radiology, Institute of Medicine, University of Tsukuba, Tsukuba, Japan.
4 Department of Biostatistics, Institute of Medicine, University of Tsukuba, Tsukuba, Japan.
5 Department of Gastrointestinal and Hepato-Biliary-Pancreatic Surgery, Institute of Medicine, University of Tsukuba, Tsukuba, Japan. Electronic address: tatoda@md.tsukuba.ac.jp.