1. Department of Biomedical EngineeringNational Cerebral and Cardiovascular Center (NCVC) Research Institute 5‐7‐1 Fujishirodai, Suita, Osaka 565‐8565 Japan
2. Department of Cardiovascular SurgeryNCVC Hospital 5‐7‐1 Fujishirodai, Suita, Osaka 565‐8565 Japan
3. Department of Materials EngineeringSchool of Engineering, The University of Tokyo 7‐3‐1 Hongo, Bunkyo‐ku, Tokyo 113‐8656 Japan
4. Medical R&D CenterCorporate R&D Group, KYOCERA Corporation 800 Ichimiyake, Yasu Shiga 520‐2362 Japan