1. Department of Radiology, Yongin Severance Hospital, Yonsei University College of Medicine, Yongin, Korea.
2. Department of Radiology, Research Institute of Radiologic Science, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Statistics, Keimyung University, Daegu, South Korea.
4. Department of Radiology, Wonju Severance Christian Hospital, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju 220-701, Korea.