1. Department of Respiratory Medicine, Weifang Yidu Central Hospital, Weifang, Shandong 262500, P.R. China
2. Department of Thoracic Surgery, The First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan 650000, P.R. China
3. Ultrasonic Department, Anqiu People's Hospital, Anqiu, Shandong 262100, P.R. China