1. Research Service, Veterans Affairs San Diego Healthcare System, San Diego, CA 92161, USA
2. Department of Radiology, University of California, San Diego, CA 92093, USA
3. Department of Neuroscience, University of California, San Diego, CA 92093, USA
4. Department of Bioengineering, University of California, San Diego, CA 92093, USA
5. Department of Bone and Joint Surgery, The First Affiliated Hospital, Jinan University, Guangzhou 510632, China
6. Radiology Service, Veterans Affairs San Diego Healthcare System, San Diego, CA 92161, USA