Norwegian Research Centre, Bergen, Norway.|Department of Mathematics, University of Bergen, Bergen, Norway.|Norwegian Research Centre, Bergen, Norway.|Norwegian Research Centre, Bergen, Norway.|Mohn Medical Imaging and Visualization Centre, Department of Radiology, Haukeland Universitetssykehus, Bergen, Norway.|Norwegian Research Centre, Bergen, Norway.|Mohn Medical Imaging and Visualization Centre, Department of Radiology, Haukeland Universitetssykehus, Bergen, Norway.|Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Germany.|Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Germany.|Department of Mathematics, University of Bergen, Bergen, Norway.