1. Department of Radiology; University of California; San Diego California USA
2. Department of Radiology; Hua Dong Hospital, Fudan University; Shanghai People's Republic of China
3. Yancheng Medical College; Jiangsu People's Republic of China
4. Department of Radiology; VA San Diego Healthcare System; San Diego California USA
5. Beijing Key Lab of Medical Physics and Engineering; Peking Univeristy; Beijing China