P Pavicevic1,2, I Dasic3, S Cvejic3. 1. Department of Radiology, University Children's Hospital, Tirsova 10, 11000, Belgrade, Serbia. pzmbov@yahoo.com. 2. Faculty of Medicine, University of Belgrade, Belgrade, Serbia. pzmbov@yahoo.com. 3. Department of Radiology, University Children's Hospital, Tirsova 10, 11000, Belgrade, Serbia.