1. From the Departments of Radiology (L.F.D.) and Pediatrics (G.M.L., P.J.S.), Stanford University School of Medicine, 180 El Camino Real, Suite M384, MC 5885, Palo Alto, CA 94304; and Department of Quality and Safety, Lucile Packard Children’s Hospital at Stanford, Palo Alto, Calif (L.F.D., G.M.L., P.J.S.).