1. Division of Advanced Surgical Science and Technology, Tohoku University Graduate School of Medicine, Sendai, Miyagi 980-8574, Japan
2. Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi 980-8574, Japan
3. Department of Cardiovascular medicine, Tohoku University Graduate School of medicine, Sendai, Miyagi, 980-8574, Japan
4. Department of Pathology, Tohoku University Hospital, Sendai, Miyagi 980-8574, Japan