1. From the Department of Radiology and Biomedical Imaging (K.M.R., H.I.G., V.A.A., N.M.H., B.N.J.) and Department of Medicine and Epidemiology (K.K., I.V.L., M.B.H.), University of California, San Francisco, 1600 Divisadero St, Room C250, San Francisco, CA 94115.