1. From the Department of Radiology (J.C.N., A.G.), Division of Orthopaedic Surgery (S.B., A.A.), and Department of Pathology and Laboratory Medicine (J.P.), Children's Hospital of Philadelphia, 3401 Civic Center Blvd, Philadelphia, PA 19104; and Department of Radiology (C.S.R.), University of Pennsylvania Perelman School of Medicine, Philadelphia, PA (J.C.N., J.P., A.A.).