1. Department of Radiology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
2. Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Radiology, Seoul Medical Center, Seoul, Korea.
4. Department of Neurology, Yonsei University College of Medicine, Seoul, Korea.