1. Department of Mechanical Engineering; Massachusetts Institute of Technology; Cambridge MA 02139 USA
2. Department of Biological Engineering; Massachusetts Institute of Technology; Cambridge MA 02139 USA
3. Laser Biomedical Research Center; Massachusetts Institute of Technology; Cambridge MA 02139 USA
4. Department of Biomedical Engineering; The Chinese University of Hong Kong; Shatin, New Territories Hong Kong SAR China
5. Central Research Laboratory; Hamamatsu Photonics K.K; Hamamatsu Shizuoka 434-8601 Japan