[1] Hokkaido Univ, Fac Med, Dept Neurosurg, Sapporo, Hokkaido, Japan
[2] Hokkaido Univ, Grad Sch Med, Sapporo, Hokkaido, Japan
[3] Hokkaido Univ Hosp, Dept Diagnost & Intervent Radiol, Sapporo, Hokkaido, Japan
[4] Sapporo Azabu Neurosurg Hosp, Dept Neurosurg, Sapporo, Hokkaido, Japan
[5] Chiba Med Ctr, Dept Neuroendovasc, Chiba, Japan
[6] Hokkaido Univ Hosp, Clin Res & Med Innovat Ctr, Sapporo, Hokkaido, Japan