1. Department of Biomedical Engineering; National Cerebral and Cardiovascular Center Research Institute; Fujishiro-dai Suita Osaka 565-8565 Japan
2. Department of Investigative Radiology; National Cerebral and Cardiovascular Center Research Institute; Fujishiro-dai Suita Osaka 565-8565 Japan
3. Faculty of Chemistry; Materials and Bioengineering; Kansai University; 3-3-35 Yamatecho Suita Osaka 565-8680 Japan