[1] Univ Cincinnati, Coll Med, Cincinnati, OH 45221 USA
[2] Cincinnati Childrens Hosp Med Ctr, Dept Radiol, 3333 Burnett Ave, Cincinnati, OH 45229 USA
[3] Cincinnati Childrens Hosp Med Ctr, Dept Pediat, Cincinnati, OH USA
[4] Harvard Med Sch, Dept Populat Med, Div Child Hlth Res & Policy, Boston, MA USA