1. Department of Diagnostic Radiology, School of Medicine, Yeungnam University, Daegu 705-717, Korea.
2. Department of Radiology, Keimyung University Dongsan Hospital, Daegu 700-712, Korea.
3. Department of Radiology, Daegu Catholic University, Daegu 705-718, Korea.
4. Department of Radiology, Dongkuk University, Kyungju, Kyungpook 780-350, Korea.