1. Department of Ultrasound, Southwest University Hospital, Chongqing 400715, P.R. China
2. Department of Abdominal Ultrasound, Xinjiang Autonomous Region Hospital of Traditional Chinese Medicine, Urumchi, Xinjiang 830000, P.R. China
3. Department of Ultrasound, Shangluo Central Hospital, Shangluo, Shaanxi 726000, P.R. China