aFrom the Department of Radiology (M.C.C.-A., C.C., M.A.B., R.A.D., J.A.E., C.J.), Boston Children's Hospital, Boston, Massachusetts

cDepartment of Radiology (M.C.C.-A., C.J.), Massachusetts General Hospital, Boston, Massachusetts

dPediatric Imaging Research Center (M.C.C.-A., C.J.), Massachusetts General Hospital, Boston, Massachusetts

eHarvard Medical School (M.C.C.-A., C.C., M.A.B., R.A.D., J.A.E., C.J.), Boston, Massachusetts