1. Department of Biomedical Engineering, School of Medicine, Boston University, Boston, MA 02215
2. Department of Anesthesiology, University of Virginia, Charlottesville, VA 22903
3. Department of Anesthesiology; Department of Biomedical Engineering, University of Iowa, Iowa City, IA 52242
4. Department of Anesthesiology and Critical Care Medicine; Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY 10065
5. Department of Anesthesiology, Biomedical Engineering, and Radiology; Department of Biomedical Engineering; Department of Radiology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242 e-mail: