1. Optical Imaging Laboratory, Department of Biomedical Engineering; Washington University in St. Louis; St. Louis, Missouri 63130 USA
2. Department of Medical Engineering; California Institute of Technology; 1200 E California Blvd., Pasadena, CA 91125
3. Department of Electrical Engineering; California Institute of Technology; 1200 E California Blvd., Pasadena, CA 91125