1 Departments of Neurological Surgery, Radiology, Neurology, Mechanical Engineering, and Stroke & Applied Neuroscience Center, University of Washington, Seattle, Washington, USA mlevitt@uw.edu.
2 Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
3 Neurology, Neurosurgery and Radiology, Rush University Medical Center, Chicago, Illinois, USA.