1. Department of Biomedical Engineering, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan.
2. Department of Investigative Radiology Advanced Medical Engineering Center, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan.
3. Japanese Science and Technology Agency–Core Research of Evolutional Science and Technology, Chiyoda-Ku, Tokyo, Japan.