1. From the Department of Radiology, Keck School of Medicine, University of Southern California, Los Angeles, Calif (S.M.N., G.R.M., D.B.P., M.S., E.A.W., A.T.); and Los Robles Radiology Associates, 227 Janss Rd, Ste 150, Thousand Oaks, CA 91360 (A.J.S.).