1. Medical Imaging Center, The Second Affiliated Hospital of Qiqihar Medical College, Qiqihar, Heilongjiang 161006, P.R. China
2. Clinical and Research Center of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, P.R. China
3. Department of Pathology, Qiqihar Medical College, Qiqihar, Heilongjiang 161006, P.R. China
4. Department of Computed Tomography, Gannan People's Hospital, Qiqihar, Heilongjiang 162100, P.R. China