1. Department of Radiology, Oita University Faculty of Medicine, Yufu, Oita, Japan
2. Department of Diagnostic Radiology, Kumamoto University Faculty of Life Sciences, Kumamoto, Kumamoto, Japan
3. Department of Radiology, Nagatomi Neurosurgical Hospital, Oita, Oita, Japan
4. Department of Radiology, Shin Beppu Hospital, Beppu, Oita, Japan
5. Department of Neurosurgery, Nagatomi Neurosurgical Hospital, Oita, Oita, Japan