1. Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan
2. Department of Neurosurgery, Teikyo University Hospital, Tokyo, Japan
3. Regenerative Medicine Research Laboratories, Fujifilm Corporation, Kanagawa, Japan
4. Division of Clinical Research Administration, Hokkaido University Hospital, Sapporo, Japan
5. Department of Neurosurgery, Graduate School of Medicine and Pharmacological Science, University of Toyama, Toyama, Japan