1. Department of Biomedical Engineering, National Cerebral and Cardiovascular Center Research Institute, Kishibe-shin Machi, Suita, Osaka 564-8565, Japan
2. Faculty of Chemistry, Materials and Bioengineering, Kansai University, 3-3-35 Yamatecho, Suita, Osaka 565-8680, Japan
3. Faculty of Medical Engineering, Suzuka University of Medical Science, Suzuka, Mie 510-0293, Japan