1. Department of Neurosurgery, Rennes University Hospital, INSERM, U746, Faculty of Medicine, INRIA, VisAGeS Unit/Project, CNRS, UMR 6074, IRISA, University of Rennes I, Rennes, France
2. Innovation Center Computer Assisted Surgery, University of Leipzig, Leipzig, Germany
3. Innovation Center Computer Assisted Surgery, University of Leipzig, Department of Neurosurgery, Leipzig University Hospital, Leipzig, Germany
4. INSERM, U746, Faculty of Medicine, INRIA, VisAGeS Unit/Project, CNRS, UMR 6074, IRISA, University of Rennes I, Rennes, France