1. From the Department of Radiology & Biomedical Imaging, University of California, San Francisco, 513 Parnassus Ave, Room S-261, Box 0628, San Francisco, CA 94143-0628 (A.M.R.); Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104 (A.M.R., J.D.R., L.X., J.W., M.T.D., A.M.K., J.E., T.C.C., I.M.N., S.M., J.C.G.); Mecklenburg Radiology Associates, Charlotte, NC (E.J.B.); and Department of Radiology, University of Texas at Austin, Austin, TX (R.N.B.).