1. Department of Radiology, Children's Hospital of Philadelphia, 3401 Civic Center Blvd, Philadelphia, PA 19104.
2. Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
3. Georgetown University, Washington, DC.
4. Department of Orthopedic Surgery, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA.
5. Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI.