1. Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710, Korea.
2. Department of Radiology, St. Mary's Hospital Catholic University, Seoul 150-713, Korea.
3. Department of Radiology, Severance Hospital Yonsei University, Seoul 120-752, Korea.
4. Department of Radiology, Ajou University Hospital, Gyeonggi-do 443-721, Korea.