1. Departments of Neurosurgery and Radiology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
2. Boston Scientific/Target, Fremont, California
3. Department of Radiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas
4. Department of Neurosurgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
5. Departments of Radiology and Neurosurgery, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas