Won Woo Lee1,2. 1. 1Department of Nuclear Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, 82, Gumi-ro 173 Beon-gil, Bundang-gu, Seongnam-si, Gyeonggi-do 13620 Korea. 2. 2Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, South Korea.