1. Department of Radiology, West China Hospital, Sichuan University, Chengdu 610041, China.
2. Department of Radiology, the Affiliated Hospital of Southwest Medical University, Luzhou 646000, China.
3. Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu 610041, China.
4. Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis 63110, MO, USA.