1. Center of Ultra-Precision Optoelectronic Instrument Engineering, Harbin Institute of Technology, Harbin, China
2. Key Laboratory of Optoelectronic Technology and Systems, Ministry of Education, Chongqing University, Chongqing, China
3. Department of Radiation Oncology, University Hospital Erlangen, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany