[1] Seattle Childrens Hosp, Dept Radiol, Seattle, WA 98105 USA
[2] Univ Washington, Dept Pediat, Harborview Med Ctr, Seattle, WA 98105 USA
[3] Vanderbilt Univ, Dept Radiol, Monroe Carell Jr Childrens Hosp, Nashville, TN USA
[4] Univ Washington, Dept Radiol, Seattle, WA 98105 USA
[5] Univ Washington, Dept Rehabil Med, Seattle, WA 98105 USA
[6] Univ Penn, Dept Pediat, Ctr Injury Res & Prevent, Childrens Hosp Philadelphia, Philadelphia, PA 19104 USA
[7] Univ Washington, Dept Epidemiol, Seattle, WA 98105 USA