1. Department of Rehabilitation Medicine, National Institutes of Health, Bethesda, MD 20892, USA
2. Department of Critical Care Medicine, National Institutes of Health, Bethesda, MD 20892, USA
3. Warren Grant Manguson Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA
4. Department of Radiology, National Institutes of Health, Bethesda, MD 20892, USA
5. National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA