1. Department of Neurosurgery, Wake Forest University School of Medicine, Winston-Salem, North Carolina;
2. Bioelectromechanical Systems Laboratory, School of Biomedical Engineering and Sciences, Virginia Tech-Wake Forest University;
3. Virginia-Maryland Regional College of Veterinary Medicine; and
4. Bioelectromechanical Systems Laboratory, Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia