1. Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, Minnesota 55455, United States
2. Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
3. Department of Surgery, University of Minnesota, 420 Delaware Street SE, Minneapolis, Minnesota 55455, United States
4. Department of Mechanical Engineering, University of Minnesota, 111 Church St. SE, Minneapolis, Minnesota 55455, United States