1. Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts;
2. Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts;
3. Department of Radiology, Beth Israel Deaconess Medical Center, Boston, Massachusetts;
4. Department of Radiology, Harvard Medical School, Boston, Massachusetts;
5. Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada;
6. Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada; and
7. Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Ontario, Canada