1. Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging; School of Biomedical Engineering; Shenzhen University; Shenzhen 518060 P. R. China
2. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province; College of Optoelectronic Engineering; Shenzhen University; Shenzhen 518060 P. R. China
3. Laboratory of Molecular Imaging and Nanomedicine; National Institute of Biomedical Imaging and Bioengineering; National Institutes of Health; Bethesda MD 20892 USA