1. Department of Thoracic Surgery, The Third Affiliated Hospital of Kunming Medical University, Kunming, Yunnan 650118, P.R. China
2. Department of Respiratory Medicine, Yan'an Affiliated Hospital of Kunming Medical University, Kunming, Yunnan 650051, P.R. China
3. Department of Ultrasonic Diagnosis, People's Hospital of Yulong County, Lijiang, Yunnan 674199, P.R. China