1 Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA.
2 Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, USA.
3 Department of Radiology, University of Iowa School of Medicine, Iowa City, Iowa, USA.
4 Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri, USA.