Fu Jin1, Juan Zhou2, Huan-Li Luo3, Ying Wang4. 1. Division of Physics, Chongqing Cancer Institute, Chongqing, People's Republic of China; Department of Radiation Oncology, Chongqing Cancer Institute, Chongqing, People's Republic of China. 2. Forensic Identification Center, College of Criminal Investigation, Southwest University of Political Science and Law, Chongqing, People's Republic of China. 3. Division of Physics, Chongqing Cancer Institute, Chongqing, People's Republic of China. 4. Department of Radiation Oncology, Chongqing Cancer Institute, Chongqing, People's Republic of China.