1. Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104;
2. Department of Neurosurgery, Hahnemann Medical College of Pennsylvania, Philadelphia, Pennsylvania 19102;
3. Departments of 3Pathology, 4Radiology, and 5Radiation and Cellular Oncology, University of Chicago, Chicago, Illinois 60637;
4. Department of Electrical and Computer Engineering, Illinois Institute of Technology, Chicago, Illinois 60616;
5. Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin 53226;