1 From the Department of Radiology, Seoul National University Hospital, Seoul National University College of Medicine, 101 Daehak-ro, Jongno-gu, Seoul 03080, Korea (S.H.Y., J.M.G.); Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea (J.M.G.); and Cancer Research Institute, Seoul National University, Seoul, Korea (J.M.G.).