1. Shanxi Provincial Key Laboratory for Biomedical Imaging and Big Data, North University of China, Taiyuan, 030051, P.R. China
2. School of Computer and Information Technology, Beijing Jiaotong University, Beijing, 100044, P.R. China
3. Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, 250117, P.R. China