1. Siemens Medical Solutions, Malvern, PA, USA
2. Department of Neurosurgery, University of Tennessee Health and Science Center, Memphis, TN, USA
3. Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN, USA
4. Vanderbilt University School of Medicine, Nashville, TN, USA
5. Cerebrovascular Program, Vanderbilt University Medical Center, Nashville, TN, USA