1 Department of NeuroradiologyFaculty of MedicineMedical Center, University of FreiburgFreiburg, Germany.
2 Departments of Radiology and Biomedical EngineeringFeinberg School of Medicine and McCormick School of EngineeringNorthwestern UniversityChicago, Illinois.
3 Institute of NeuroradiologyHirslanden Clinic ZurichZurich, Switzerland.