[1] Okayama Univ, Sch Med, Dept Publ Hlth, Okayama 7008558, Japan
[2] Kawasaki Med Sch Hosp, Dept Gastroenterol 1, Okayama 7010114, Japan
[3] Kawasaki Med Sch Hosp, Dept Diagnost Radiol, Okayama 7010114, Japan
[4] Yura Hosp, Okayama 7060023, Japan
[5] Shigei Med Res Hosp, Okayama 7010202, Japan