1. Department of Radiology, KyungHee University Medical Center, KyungHee University College of Medicine, Seoul, Korea.
2. Department of Radiology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Neurosurgery, Dongguk University Ilsan Hospital, Dongguk University College of Medicine, Goyang, Korea.
4. Department of Neurosurgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
5. Department of Radiology, Veterans Health Service Medical Center, Seoul, Korea.