1. Department of Neurosurgery, Karolinska University Hospital, and Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden;
2. Philips Research, High Tech Campus 34, Eindhoven;
3. Eindhoven University of Technology (TU/e), Eindhoven;
4. Philips Healthcare, Best; and
5. Department of Biomechanical Engineering, Delft University of Technology, Delft, The Netherlands