1 From the Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongro-Gu, Seoul 03080, South Korea (J.H.Y., J.M.L.); Department of Radiology, Seoul National University College of Medicine, Seoul, South Korea (J.H.Y., J.M.L.); and Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, South Korea (J.M.L.).