1. Department of Mathematics, Southeast University, Nanjing 210096, P. R. China
2. Mathematical Sciences Department, Worcester Polytechnic Institute, Worcester, MA 01609, USA
3. Department of Medicine, Emory University School of Medicine, Atlanta, GA 30307, USA
4. Mallinckrodt Institute of Radiology, Washington University, St. Louis, MO 63110, USA
5. The Cardiovascular Research Foundation, Columbia University, New York, NY 10022, USA
6. School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, P. R. China
7. Department of Cardiology, Zhongda Hospital, Southeast University Nanjing 210009, P. R. China
8. The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA