| 1. | Qi X, Berzigotti A, Cardenas A, et al. Emerging non-invasive approaches for diagnosis and monitoring of portal hypertension. Lancet Gastroenterol Hepatol, 2018, 3(10): 708-719. | 
				                                                        
				                                                            
				                                                                | 2. | 宋珂达, 姜洪池. 门静脉压力无创测定应给予重视. 中华普通外科学文献(电子版), 2018, 12(6): 373-375. | 
				                                                        
				                                                            
				                                                                | 3. | Bolognesi M, Di Pascoli M, Sacerdoti D. Clinical role of non-invasive assessment of portal hypertension. World J Gastroenterol, 2017, 23(1): 15-24. | 
				                                                        
				                                                            
				                                                                | 4. | Ravaioli F, Montagnani M, Lisotti A, et al. Noninvasive assessment of portal hypertension in advanced chronic liver disease: An update. Gastroenterol Res Prac, 2018, 2018: 1-11. | 
				                                                        
				                                                            
				                                                                | 5. | Thabut D, Moreau R, Lebrec D. Noninvasive assessment of portal hypertension in patients with cirrhosis. Hepatology, 2011, 53(2): 683-694. | 
				                                                        
				                                                            
				                                                                | 6. | Addley J, Tham T C, Cash W J. Use of portal pressure studies in the management of variceal haemorrhage. World J Gastrointest Endosc, 2012, 4(7): 281-289. | 
				                                                        
				                                                            
				                                                                | 7. | Leung J C-F, Loong T C-W, Pang J, et al. Invasive and non-invasive assessment of portal hypertension. Hepatol Int, 2018, 12: 44-55. | 
				                                                        
				                                                            
				                                                                | 8. | Levick C, Phillips-Hughes J, Collier J, et al. Non-invasive assessment of portal hypertension by multi-parametric magnetic resonance imaging of the spleen: A proof of concept study. PLoS ONE, 2019, 14(8): e0221066. | 
				                                                        
				                                                            
				                                                                | 9. | Wang J, Gao F, Shen J L. Noninvasive assessment of portal hypertension using spectral computed tomography. J Clin Gastroenterol, 2019, 53(9): e387-e391. | 
				                                                        
				                                                            
				                                                                | 10. | Roccarina D, Rosselli M, Genesca J, et al. Elastography methods for the non-invasive assessment of portal hypertension. Expert Rev Gastroenterol Hepatol, 2018, 12(2): 155-164. | 
				                                                        
				                                                            
				                                                                | 11. | Elmahdy A M, Berzigotti A. Non-invasive measurement of portal pressure. Curr Hepat Rep, 2019, 18: 20-27. | 
				                                                        
				                                                            
				                                                                | 12. | Leeming D J, Veidal S S, Karsdal M A, et al. Pro-C5, a marker of true type V collagen formation and fibrillation, correlates with portal hypertension in patients with alcoholic cirrhosis. Scand J Gastroenterol, 2015, 50(5): 584-592. | 
				                                                        
				                                                            
				                                                                | 13. | La Mura V, Reverter J C, Flores-Arroyo A, et al. Von Willebrand factor levels predict clinical outcome in patients with cirrhosis and portal hypertension. Gut, 2011, 60(8): 1133-1138. | 
				                                                        
				                                                            
				                                                                | 14. | Zhang Q W, Wang Y, Wang J, et al. A non-invasive magnetic resonance imaging-based model predicts portal venous pressure. J Digest Dis, 2016, 17(3): 175-185. | 
				                                                        
				                                                            
				                                                                | 15. | Chen J, Yin M, Talwalkar J A, et al. Diagnostic performance of MR elastography and vibration-controlled transient elastography in the detection of hepatic fibrosis in patients with severe to morbid obesity. Radiology, 2016: 160685. | 
				                                                        
				                                                            
				                                                                | 16. | Andaluz I, Abadía M, Ponce D, et al. SAT-409-Hepatic vein arrival time assessed by contrast-enhanced ultrasound in the non-invasive evaluation of portal hypertension. J Hepatol, 2019, 70(1): e813. | 
				                                                        
				                                                            
				                                                                | 17. | Ferraioli G, Tinelli C, Dal Bello B, et al. Accuracy of real-time shear wave elastography for assessing liver fibrosis in chronic hepatitis C: A pilot study. Hepatology, 2012, 56(6): 2125-2133. | 
				                                                        
				                                                            
				                                                                | 18. | Xie Limei. Real-time elastography for diagnosis of liver fibrosis in chronic hepatitis B. J Ultrasound Med, 2012, 31(7): 1053-1060. | 
				                                                        
				                                                            
				                                                                | 19. | Wiechowska-Kozłowska A, Zasada K, Milkiewicz M, et al. Correlation between endosonographic and Doppler ultrasound features of portal hypertension in patients with cirrhosis. Gastroenterol Res Prac, 2012, 2012(1): 395345. | 
				                                                        
				                                                            
				                                                                | 20. | Elwan N, Salah R, Hamisa M, et al. Evaluation of portal pressure by Doppler ultrasound in patients with cirrhosis before and after simvastatin administration - a randomized controlled trial. F1000 Res, 2018, 7: 256. | 
				                                                        
				                                                            
				                                                                | 21. | Postema M, Gilja O H. Contrast-enhanced and targeted ultrasound. World J Gastroenterol, 2011, 17(1): 28-41. | 
				                                                        
				                                                            
				                                                                | 22. | Jansen C, Bogs C, Verlinden W, et al. Shear-wave elastography of the liver and spleen identifies clinically significant portal hypertension: A prospective multicentre study. Liver Int, 2017, 37(3): 396-405. | 
				                                                        
				                                                            
				                                                                | 23. | 吕道文, 张拥军, 赵挺, 等. 超声造影剂微泡次谐波辅助压力估测技术研究进展. 中国医学物理学杂志, 2016, 33(9): 959-962. | 
				                                                        
				                                                            
				                                                                | 24. | Eisenbrey J R, Dave J K, Halldorsdottir V G, et al. Chronic liver disease: Noninvasive subharmonic aided pressure estimation of hepatic venous pressure gradient. Radiology, 2013, 268(2): 581-588. | 
				                                                        
				                                                            
				                                                                | 25. | Li F, Li D, Yan F. Improvement of detection sensitivity of microbubbles as sensors to detect ambient pressure. Sensors, 2018, 18(12): 4083. | 
				                                                        
				                                                            
				                                                                | 26. | Shi W T, Forsberg F, Raichlen J S, et al. Pressure dependence of subharmonic signals from contrast microbubbles. Ultrasound Med Biol, 1999, 25(2): 275-283. | 
				                                                        
				                                                            
				                                                                | 27. | Leodore L M, Forsberg F, Shi W T. P5B-6 in vitro pressure estimation obtained from subharmonic contrast microbubble signals//2007 IEEE Ultrasonics Symposium. New York: IEEE, 2007: 2207-2210. | 
				                                                        
				                                                            
				                                                                | 28. | Andersen K S, Jensen J A. Impact of acoustic pressure on ambient pressure estimation using ultrasound contrast agent. Ultrasonics, 2010, 50(2): 294-299. | 
				                                                        
				                                                            
				                                                                | 29. | Sun T, Jia N, Zhang D, et al. Ambient pressure dependence of the ultra-harmonic response from contrast microbubbles. J Acoust Soc Am, 2012, 131(6): 4358. | 
				                                                        
				                                                            
				                                                                | 30. | Wu Jun, Fan Tingbo, Xu Di, et al. Investigation on the relationship between overpressure and sub-harmonic response from encapsulated microbubbles. Chin Phys B, 2014, 23(10): 104302. | 
				                                                        
				                                                            
				                                                                | 31. | 李德玉, 李飞, 樊瑜波, 等. 基于微泡超声造影剂的血压无创测量装置: CN101982156B. 2010. | 
				                                                        
				                                                            
				                                                                | 32. | 李飞. 基于超声造影剂次谐波的无创血压测量方法研究. 北京: 北京航空航天大学, 2012. | 
				                                                        
				                                                            
				                                                                | 33. | Dave J K, Halldorsdottir V G, Eisenbrey J R, et al. Noninvasive LV pressure estimation using subharmonic emissions from microbubbles. JACC-Cardiovasc Imag, 2012, 5(1): 7-92. | 
				                                                        
				                                                            
				                                                                | 34. | 黄韫栀, 刘奇, 肖勇. 基于超声RF信号的超声成像实验设计. 实验科学与技术, 2016, 14(6): 32-35, 84. | 
				                                                        
				                                                            
				                                                                | 35. | 周志华. 机器学习. 北京: 清华大学出版社, 2016. |