Affiliation: | (1) Department of Pediatric Rheumatology, Kinder- und Rheumakinderklinik, Garmisch-Partenkirchen, Germany;(2) Department of Radiology, Children's Memorial Hospital, Chicago, Illinois, USA;(3) Northwestern University Medical School, Chicago, Illinois, USA;(4) Department of Statistics, Northwestern University, Evanston, Illinois, USA |