1. From the Departments of Radiology (Y.G., K.C.) and Neurology (H.L., G.-Y.Y.), Ruijin Hospital, School of Medicine, Shanghai, China; Med-X Research Institute and School of Biomedical Engineering (Y.W., F.Y., H.L., G.-Y.Y.), Shanghai Jiao Tong University, Shanghai, China; Shanghai Institute of Applied Physics (Y.R., T.X.), Chinese Academy of Sciences, Shanghai, China; and the Buck Institute for Age Research (D.A.G., K.J.), Novato, CA.