1. Department of Radiology, China-Japan Friendship Hospital, Beijing 100029, China
2. School of Medicine, University of California, San Diego (UCSD), San Diego, CA 92093, USA
3. Department of Radiology, Beijing Jishuitan Hospital, Beijing 100035, China
4. Department of Radiology, Second Affiliated Hospital, Harbin Medical University, Harbin 150086, China