1. Department of Radiology and Imaging Sciences, University of Utah Health Sciences Center, 30 N 1900 E, #1A071, Salt Lake City, UT 84132-2140.
2. Department of Radiology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY.
3. Department of Radiology, Division of Neuroradiology, Spine Intervention Service, Duke University Medical Center, Durham, NC.
4. Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
5. Department of Radiology, Division of Neuroradiology, Duke University Medical Center, Durham, NC.