1. Graduate School of Health Sciences, Hokkaido University , N12-W5, Kita-ku, Sapporo 060-0812 , Japan
2. Department of Radiology, Sapporo Shuyukai Hosipital , 6-2-1, Shinhassamu 5-jo, Teine-ku, Sapporo 006-0805 , Japan
3. Department of Neurosurgery, Sapporo Shuyukai Hospital , 6-2-1, Shinhassamu 5-jo, Teine-ku, Sapporo 006-0805 , Japan
4. Department of Radiology, Sapporo Higashi Tokushukai Hospital , N33-E14, Higashi-ku, Sapporo 065-0033 , Japan
5. Department of Radiological Technology , Faculty of Health Sciences, , 15-4-1, Maeda 7-jo, Teine-ku, Sapporo 006-8585 , Japan
6. Hokkaido University of Science , Faculty of Health Sciences, , 15-4-1, Maeda 7-jo, Teine-ku, Sapporo 006-8585 , Japan
7. Faculty of Health Sciences, Hokkaido University , N12-W5, Kita-ku, Sapporo 060-0812 , Japan