1. Institute of Biomedical Sciences, School of Physics and Electronics, Shandong Normal University, Jinan, Shandong, People’s Republic of China;
2. Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Jinan, Shandong, People’s Republic of China;
3. Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Jinan, Shandong, People’s Republic of China;
4. Department of Medical Imaging, Jinan Military General Hospital, Jinan, Shandong, People’s Republic of China