1. Department of Anesthesiology, The First Affiliated Hospital of Hebei North University, Zhangjiakou, Hebei 075000, P.R. China
2. Department of Medical Imaging, The First Affiliated Hospital of Hebei North University, Zhangjiakou, Hebei 075000, P.R. China
3. Department of Ultrasound, The First Affiliated Hospital of Hebei North University, Zhangjiakou, Hebei 075000, P.R. China
4. Department of Operating Room, The First Affiliated Hospital of Hebei North University, Zhangjiakou, Hebei 075000, P.R. China