Xiaoqin Zhang1, Yi Wu2. 1. Department of Digital Medicine, College of Biomedical Engineering and Medical Imaging, Army Medical University (Third Military Medical University), Chongqing, 400038, China. 2. Department of Digital Medicine, College of Biomedical Engineering and Medical Imaging, Army Medical University (Third Military Medical University), Chongqing, 400038, China. wuy1979@tmmu.edu.cn.