1. Warren Alpert Medical School Brown University Providence RI USA
2. Department of Radiology and Biomedical Imaging Yale University New Haven CT USA
3. National Institute of Neurological Disorders and Stroke National Institutes of Health Bethesda MD USA
4. Division of Interventional Neuroradiology, Department of Radiology University of Maryland Medical Center Baltimore MD USA
5. Department of Neurology Georgetown University Hospital Washington DC USA