1. School of Automation, Xi'an University of Posts and Telecommunications, Xi'an, Shanxi, China
2. Institute of Image Processing & Pattern Recognition, Xi'an Jiaotong University, Xi'an, Shanxi, China
3. Department of Radiology, Division of Radiologic Sciences, Wake Forest University Health Sciences, Winston-Salem, NC, USA
4. Biomedical Imaging Division, VT-WFU School of Biomedical Engineering and Sciences, Wake Forest University Health Sciences, Winston-Salem, NC, USA