1. From the Departments of Radiology (B.T., M.D.N.) and Pediatrics (M.B.N., G.D.), Children’s Hospital Los Angeles, 4650 Sunset Blvd, MS 81, Los Angeles, CA 90027; and Departments of Radiology (C.S.J.L.), Neurology and Radiology (S.Y.C.), and Pediatrics (M.B.N.), Keck School of Medicine of the University of Southern California, Los Angeles, Calif.