1. Department of Ultrasound; the First Affiliated Hospital of Chongqing Medical University; Chongqing 400010 China
2. Pediatric Research Institute; Children's Hospital of Chongqing Medical University; Chongqing 400014 China
3. Institute of Ultrasound Imaging; the Second Affiliated Hospital of Chongqing Medical University; Chongqing 400010 China
4. State Key Laboratory of High Performance Ceramics and Superfine Microstructures; Shanghai Institute of Ceramics; Chinese Academy of Sciences; Shanghai 200050 China