1. Department of Internal Medicine, Seoul National University, Seoul, Korea.
2. Department of Internal Medicine, Bundang Hospital, Seoul National University, Seoul, Korea.
3. Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, Korea.
4. Department of Internal Medicine, Chung-Ang University Hospital, Seoul, Korea.
5. Department of Internal Medicine, Boramae Medical Center; Seoul National University, Seoul, Korea.