1. Department of Neurosurgery, Tohoku University Graduate School of Medicine , Sendai 980-8574 , Japan
2. Department of Radiation Oncology, Tohoku University Graduate School of Medicine , Sendai 980-8574 , Japan
3. Department of Behavioral and Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine , Sendai 980-8574 , Japan
4. Department of Diagnostic Radiology, Tohoku University Graduate School of Medicine , Sendai 980-8574 , Japan
5. Department of Radiology, Iwate Medical University School of Medicine , Iwate 028-3694 , Japan
6. Department of Neurosurgery, Nagoya University Graduate School of Medicine , Sendai 466-8550 , Japan
7. Department of Neurosurgery, Yamagata University School of Medicine , Yamagata 990-9585 , Japan
8. Department of Neurosurgery, Kitasato University School of Medicine , Sagamihara 252-0374 , Japan