1Division of Radiological Physics, Deparment of Radiology, University Hospital of Basel, Basel, Switzerland, 2Department of Biomedical Engineering, University of Basel, Basel, Switzerland, 3Department of Pediatric Pneumology, University Children's Hospital Basel (UKBB), Basel, Switzerland, 4Division of Respiratory Medicine, Department of Pediatrics, University Children's Hospital of Bern, Bern, Switzerland, 5Institute of Diagnostic Radiology, Interventional Radiology and Nuclear Medicine, Ruhr-University of Bochum, Bochum, Germany, 6Department of Pediatric Pneumology, University Children's Hospital of Ruhr University Bochum at St Josef-Hospital, Bochum, Germany