国家自然科学基金(81341066)%北京市卫生系统高层次卫生技术人才基金(2013-2-003)%北京安贞医院院长科技发展基金(2013Z03)。This study was supported by the National Natural Science Foundation of China(81341066)%Beijing Health System Special Foundation for Build-ing High-level Health Personnel(2013-2-003)%The Science and Technology Development Foundation of Anzhen Hospital(2013Z03)