1. From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 1825 4th St, Room L3185, San Francisco, CA, 94107 (M.C., J.H.H., A.K., H.I.G., K.M.R., B.N.J., A.Y.L.); and Department of Radiology, Mayo Clinic, Rochester, Minn (G.A.W.).