1 Department of radiology, the Second Affiliated Hospital of Baotou Medical College, Inner Mongolia University of Science and Technology, Baotou 014030, China.
2 Department of public health, Baotou City Center for Disease Control and Prevention, Baotou, China.
3 Department of radiology, the Second Affiliated Hospital of Baotou Medical College, Inner Mongolia University of Science and Technology, Baotou 014030, China. Electronic address: jiqingyusci@163.com.