1. School of Computer Science and Technology, Shandong University of Finance and Economics, Jinan, Shangdong, China
2. Medical Physics Division in the Department of Radiation Oncology, Stanford University, Palo Alto, CA, USA
3. Digital Media Technology Key Lab of Shandong Province, Jinan, Shandong, China
4. School of Computer Science and Technology, Shandong University, Jinan, Shandong, China