1. Department of Radiology, Hallym University Sacred Heart Hospital, Gyeonggi-do 431-070, Korea.
2. Department of Radiology and Research Institute of Radiological Science, Severance Hospital, University of Yonsei, College of Medicine, Seoul 120-752, Korea.
3. Department of Radiology, Inje University Ilsan Paik Hospital, Gyeonggi-do 411-706, Korea.
4. Department of Radiology, Gangnam Severance Hospital, University of Yonsei, College of Medicine, Seoul 135-720, Korea.