1. Metabolism Unit, Massachusetts General Hospital and Harvard Medical School , Boston, Massachusetts , USA
2. Liver Center, Gastroenterology Division, Massachusetts General Hospital and Harvard Medical School , Boston, Massachusetts , USA
3. Department of Radiology, Massachusetts General Hospital and Harvard Medical School , Boston, Massachusetts , USA
4. Laboratory of Pathology, Center for Cancer Research, National Cancer Institute , Bethesda, Maryland , USA
5. National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, Maryland , USA