1. From the Department of Radiology, Seoul National University Bundang Hospital, 82 Gumi-ro 173 Beon-gil, Bundang-gu, Seongnam-si, Gyeonggi-do, 13620 Seongnam, Korea (H.Y.K., J.H.P., Y.J.L., S.S.L., K.H.L.); and Department of Statistics, University of Seoul, Seoul, Korea (J.J.J.).