1. From the Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, 9609 Medical Center Dr, NCI Shady Grove Room 7E536, Bethesda, MD 20892-9778 (M.S.L.); Department of Pediatrics, School of Medicine, Case Western Reserve University, Cleveland, Ohio (P.B.D.); and Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Mass (J.A.B.).