1. Department of Radiology, Korea University College of Medicine, Ansan Hospital, Ansan, Korea.
2. Department of Pediatrics, Korea University College of Medicine, Ansan Hospital, Ansan, Korea.
3. Department of Biostatistics, Korea University College of Medicine, Seoul, Korea.
4. Department of Radiology, Inje University College of Medicine, Ilsan Paik Hospital, Goyang, Korea.