1. Department of Radiation Oncology; University of Texas Southwestern Medical Center; Dallas, TX 75235 USA
2. Institute of Image Processing and Pattern Recognition; Xi'an Jiaotong University; Xi'an Shaanxi 710049 China
3. Beijing Center for Mathematics and Information Interdisciplinary Sciences; Beijing 10048 China
4. Cyber Medical Corporation; Xi'an Shaanxi 710018 China
5. School of Biomedical Engineering; Southern Medical University; Guangzhou Guangdong 510515 China
6. Zhujiang Hospital; Southern Medical University; Guangzhou Guangdong 510515 China