[1] Chiba Univ, Dept Orthopaed Surg, Grad Sch Med, Chuou Ku, 1-8-1 Inohana, Chiba, Chiba 2608670, Japan
[2] Chiba Univ Hosp, Dept Radiol, Chuou Ku, 1-8-1 Inohana, Chiba, Chiba 2600856, Japan
[3] Natl Inst Radiol Sci, Ctr Charged Particle Therapy, Inage Ku, 4-9-1 Anagawa, Chiba, Chiba 2638555, Japan
[4] Univ Tsukuba, Dept Orthopaed Surg, Fac Med, 1-1-1 Tennodai, Tsukuba, Ibaraki 3058577, Japan