1. City College of the City University of New York, Department of Biomedical Engineering, 160 Convent Avenue, New York, New York 10031
2. City College of the City University of New York, Department of Physics, Institute for Ultrafast Spectroscopy and Lasers, 160 Convent Avenue, New York, New York 10031
3. Washington University in St. Louis, Department of Radiology, School of Medicine, 4525 Scott Avenue, St. Louis, Missouri 63110
4. City College of the City University of New York, Department of Physics, Institute for Ultrafast Spectroscopy and Lasers, 160 Convent Avenue, New York, New York 10031dUniversidade de São Paulo, Instituto de Física de São Carlos, São Carlos 13566-590, Brazi