1. From the Department of Radiology, Severance Hospital (K.H., J.H.K., G.M.K., J.L., J.Y.W., M.D.K.), Department of Anesthesiology and Pain Medicine, Anesthesia and Pain Research Institute (S.Y.K., H.J.K., E.J.Y.), and Biostatistics Collaboration Unit, Department of Biomedical Systems Informatics (H.J.S.), Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea.