Non-invasive assessment of liver fibrosis in a rat model: shear wave elasticity imaging versus real-time elastography.

The purpose of this study was to investigate the diagnostic value of shear wave elasticity imaging (SWEI) and real-time elastography (RTE) in liver fibrosis induced by dimethylnitrosamine (DMN) and to compare the accuracy of these methods. Seventy male Wistar rats given a single intra-peritoneal injection of DMN and 10 control rats given a saline injection underwent SWEI and RTE to determine their shear wave velocity (V(s)) and liver fibrosis (LF) index, respectively. Correlations between V(s) or the LF index and histologic stage of liver fibrosis (S0-S4) were analyzed, and the diagnostic values of the techniques were assessed using a receiver operating characteristic curve. A positive correlation was found between V(s) and stage of liver fibrosis (r = 0.947, p < 0.001) and between LF index and stage (S) of liver fibrosis (r = 0.662, p < 0.001). For Vs, the areas under the receiver operating characteristic curve for the diagnosis of fibrosis, S ≥ S1, S ≥ S2, S ≥ S3 and S = S4, were 0.983, 0.995, 0.999 and 0.964, respectively; for the LF index, the values were 0.871, 0.887, 0.761 and 0.839, respectively (all p < 0.001). Vs and the LF index values in rats with severe inflammatory activity were significantly higher than those in controls (p < 0.001). In conclusion, positive correlations exist between V(s) or the LF index and the severity of liver fibrosis in rats. Vs is more accurate than the LF index in predicting liver fibrosis in rats. However, severe inflammatory activity may reduce the accuracy of both techniques.

[Real-time elastography for quantitative assessment of liver fibrosis in a rat model].

OBJECTIVE: To investigate the feasibility of real-time elastography for quantitative evaluation of liver fibrosis in a rat model. METHODS: A total of 70 male Wistar rats were included in the group for dimethylnitrosamine (DMN)-induced liver injury, and 10 saline-injected rats were used as normal control. Hepatic injury was induced by a single intraperitoneal injection of DMN at a dose of 50 mg/kg of body weight. Nine or ten rats in the group with DNM injected and one or two rats in the normal control group were randomly selected and sacrificed at each of the following post-injection time: day 5, 7, 10, 14, 21, 24, and 28. And their livers were taken for pathology analysis. All the rats underwent real-time elastography before sacrificed in order to acquire area ratio of low-strain region (% AREA) and liver fibrosis index (LF index) which were compared with the stage of liver fibrosis and grade of necroinflammatory pathologically. By the different data, Spearman correlation analysis, rank-sum test or receiver operating characteristic curve was used. RESULTS: Among 58 successfully modeled rats, there were nine, 13, 14 and 12 rats of S1, S2, S3 and S4 liver fibrosis on pathology, respectively, which were with or without mild necroinflammatory. The other 10 rats were found to be S0 with severe necroinflammatory. Values of LF index and % AREA both increased with liver fibrosis stage (P less than 0.05). There was certain correlation between LF index and liver fibrosis stage (r=0.643, P=0.000), so was % AREA and liver fibrosis stage (r=0.662, P=0.000). As for LF index, Areas under the receiver operating characteristic curve (Az) was 0.943, 0.890, 0.743 and 0.821 for the diagnosis of hepatic fibrosis S1 or higher, S2 or higher, S3 or higher and S4, respectively; as for % AREA, they were 0.948, 0.883, 0.772 and 0.842, respectively. However, we found a significant difference for LF index or % AREA between S0 with and without severe inflammatory activity rats (P=0.005 and P=0.017). CONCLUSION: Real-time elastography is available for quantitative assessment of liver fibrosis in rats induced by DMN, but severe inflammatory activity can affect its accuracy.