1 Department of Radiology, Hongqi Hospital affiliated to Mudanjiang Medical University, Mudanjiang City, Heilongjiang Province 157000, China.
2 Department of Radiology, The Second Affiliated to Mudanjiang Medical University, Dongxiaoyun 3 Street, Mudanjiang City, Heilongjiang Province 157000, China. Electronic address: zhaozijunnannan@yeah.net.