| Objective: 2D SWE(two dimensional shear wave elastography)has become an important method to assess the degree of liver fibrosis,guide the treatment,prognosis and follow-up monitoring of patients with chronic liver disease.With the widespread application of this technology in the clinic,the repeatability of measurement has become a concern of the majority of ultrasound workers.The purpose of this study is to evaluate the repeatability of liver stiffness measurements obtained by two dimensional shear wave elastography.To analyze the effect of operator experience,measurement conditions and pathophysiology factors on repeatability,so as to provide strong evidence of this technology in measurement methodology.To discuss the application value in non-alcoholic fatty liver disease by comparing the difference of Young's modulus of liver between patients with different degrees of non-alcoholic fatty liver and patients with or without fatty hepatitis.Methods: Part one included 423 patients,who with chronic liver disease(including viral hepatitis disease,alcoholic liver disease,nonalcoholic fatty liver disease etc)and undergone liver ultrasound elastography in our hospital.Regardless of liver function status,only patients with failed measurements were excluded.This study was completed by 2 operators.Each patient was measured by two operators for three consecutive times.The mean elasticity values were recorded when the measured diameter was adjusted to 10,20,and 30 mm.Operator A had more than 5 years of experience in routine abdominal US examinations and had successfully performed approximately 10,000 2D SWE examinations.Operator B is a novice who had been studying ultrasound for 5 months.Before this study,operator A trained operator B.The measurement was considered to be invalid when there was no or little filling in the sampling frame(filling area < Q-box size when diameter is 20 mm).The failure of three consecutive times signified this examination fail.The median values of three effective measurements were recorded for statistical analysis.Intraclass correlation coefficient(ICC),coefficient of variation(CV)and Bland-Altman plots of operators A and B were calculated respectively for different measurement diameters.The effect of operator experience and measurement diameter on repeatability was analyzed.All patients were divided into groups according to sex,age,prehepatic fat thickness and ascites.The effect of these factors on the repeatability within and between groups was analyzed.The objects of the second part were divided into two groups.Group 1 included 138 patients with fatty liver from January to September 2017.All patients undergone routine ultrasound and 2D SWE.All patients were examined by two operators and divided into three subgroups: mild,moderate and severe degree.There were 38 cases of mild fatty liver,65 cases of moderate fatty liver,35 cases of severe fatty liver,50 cases of control group.Patients with history of other liver disease,long-term drinking history,medication history and liver dysfunction were excluded.The liver Young's modulus of different groups of patients was statistically analyzed,and the differences between the groups were compared.In group 2,50 NAFLD patients who had underwent liver biopsy in our hospital from January 2015 were collected.All patients undergone routine ultrasound and 2D SWE.There were 28 patients with simple fatty liver group and 22 patients with nonalcoholic steatohepatitis(NASH group).The differences in liver Young's modulus values and liver function serological indexes between the two groups were compared,and the ROC curve was drawn to analyze the value of each index in the diagnosis of steatohepatitis.The risk factors of NASH were predicted by Logistic regression analysis.Results: 1.Operator A's measurement repeatability was significantly higher than that of Operator B,and the difference was statistically significant(P<0.05).The ICC of operators within or between groups were greater than 0.9,indicating a high measurement repeatability.2.The ICC values were similar between the 10-and 20mm-diameter groups,which has no statistically significant difference(P>0.05).The ICC values in the 30mm-diameter group was the lowest,which has statistically significant difference(P<0.05).3.The Bland-Altman plots showed that the difference between operators was low for the 10-,20mm-diameter groups(LOA ? 3 k Pa);the difference between operators was high for the 30mm-diameter groups(LOA>3 k Pa).4.ICC was higher in male than female;ICC was higher in the elder;ICC was higher when prehepatic tissue is thicker;ICC was higher when pre-liver fluid exits.The differences within groups were statistically significant(P<0.05).5.The difference was statistically significant between control group and fatty liver group(F=3.843,P<0.05);the difference was statistically significant between control group and moderate groups(P<0.05).the difference was statistically significant between control group and severe group(P< 0.05)the difference was statistically significant between mild group and severe group(P< 0.05).6.The young's modulus of liver was(4.43 ± 0.47)k Pa in simple fatty liver group and(5.99±2.0)k Pa in NASH group.The difference between the two groups was statistically significant(t =-3.93,P<0.01).NASH and simple fatty liver group were distinguished by young's modulus,and ROC curve was drawn.The area under the curve was 0.844.The sensitivity and specificity was 77.2%?96.4% when the diagnostic threshold was 5.1kpa.7.Compared with the serological parameters of patients in NASH group and simple fatty liver group,the differences in ALT,AST,and TBIL were statistically significant,and the differences in ALP and GGT were not statistically significant.NASH and simple fatty liver were distinguished by ALT,AST,and TBIL,and ROC curves were drawn.The areas under the curves were 0.805,0.795,and 0.755,which were lower than the areas under the ROC curve drawn by the Young's modulus of the liver,which has no statistically significant difference(P>0.05).8.Logistic regression analysis showed that ALT and liver Young's modulus were independent risk factors for NASH.Conclusion: In summary,1.This study shows 2D SWE has a high measurement repeatability,experienced operators have better measurement repeatability than beginners.2.The measurement diameter has an influence on the measurement repeatability.The measurement repeatability is the lowest when the measurement diameter is 30 mm.The measurement repeatability is similar when the measurement diameter is 10 mm and 20 mm.3.The subject's sex,age,thickness of prehepatic tissue and prehepatic fluid also influence the repeatability.4.With the increase of ultrasonic graduation in NAFLD patients,the value of liver Young's modulus gradually decreases.5.2D SWE has certain clinical significance in distinguishing NASH and simple fatty liver.When the diagnostic threshold is 5.1 k Pa,the sensitivity and specificity is relatively high.6.Logistic regression analysis showed that ALT and liver Young's modulus were independent risk factors for NASH. |
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