1. Department of Neurosurgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.
2. Department of Radiology, St. Vincent's Hospital, The Catholic University of Korea, Suwon, Korea.
3. Department of Radiology, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
4. Department of Radiology, NHIC Ilsan Hospital of Korea, Ilsan, Korea.
5. Department of Radiology, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.