1. Department of Ultrasound, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
2. Department of Thoracic Surgery, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China
3. Department of Orthopedics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China
4. Department of General Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China