1. Department of Radiology, Seoul St. Mary's Hospital, Seoul 137-701, Korea.
2. Department of Radiology, St. Vincent Hospital, Gyeonggi-do 442-723, Korea.
3. Department of Radiology, Uijeongbu St. Mary's Hospital, Gyeonggi-do 480-821, Korea.
4. Department of Radiology, Bucheon St. Mary's Hospital, Gyeonggi-do 420-717, Korea.
5. Department of Radiology, Yeouido St. Mary's Hospital, School of Medicine, The Catholic University of Korea, Seoul 150-713, Korea.