Viscoelasticity measured by shear wave elastography in a rat model of nonalcoholic fatty liver disease: comparison with dynamic mechanical analysis

Abstract

Background Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming one of the most common liver diseases. Ultrasound elastography has been used for the diagnosis of NAFLD. However, clinical research on steatosis by elastography technology has mainly focused on steatosis with fibrosis or non-alcoholic steatohepatitis (NASH), while steatosis without fibrosis has been poorly studied. Moreover, the relationship between liver viscoelasticity and steatosis grade is not clear. In this study, we evaluated the degree of liver steatosis in a simple steatosis rat model using shear wave elastography (SWE). Results The viscoelasticity values of 69 rats with hepatic steatosis were measured quantitatively by SWE in vivo and validated by a dynamic mechanical analysis (DMA) test. Pathological sections were used to determine the steatosis grade for each rat. The results showed that the elasticity values µ obtained by the two methods followed the same trend, and µ is significantly correlated with liver steatosis. The Pearson’s correlation coefficients indicate that $$\mu$$ μ obtained by SWE is positively linear correlated with DMA (r = 0.628, p = 7.85 × 10–9). However, the viscosity values $$\eta$$ η obtained by SWE were relatively independent of those obtained by DMA with a correlation coefficient of − 0.01. The combined Voigt elasticity measurements have high validity in the prediction of steatosis (S0 vs. S1–S4), with an AUROC of 0.755 (95% CI 0.6175–0.8925, p < 0.01) and the optimal cutoff value was 2.08 kPa with a sensitivity of 78% and specificity of 63%. Conclusion SWE might have the feasibility to be introduced as an auxiliary technique for NAFLD patients in clinical settings. However, the viscosity results measured by SWE and DMA are significantly different, because the two methods work in different frequency bands.

Bioinspired Bioinks for the Fabrication of Chemomechanically Relevant Standalone Disease Models of Hepatic Steatosis

“…[ 39–41 ] However, the accumulation of lipids that characterizes NAFLD enhances the viscous behavior of the surrounding tissue. [ 41–43 ] This peculiar aspect is due to the viscosity of triglycerides being significantly higher than the one of water. [ 44 ] In light of these, s‐Hep3Gel effectively mimics the biomechanics of hepatic steatosis, as the values of G′ and G″ are coherent with those proposed by literature.…”

Diagnostic efficiency on ultrasound shear wave elastography in evaluation of steatosis severity for non-alcoholic fatty liver disease: a rat model

“…SWE can quantitatively reflect tissue stiffness according to shear wave propagation in the tissue expressed as Young's modulus. Zhaoke Pi et al [ 28 ] showed that the elasticity values µ attained by SWE in vivo had a significant correlation with liver steatosis in NAFLD in a mouse model. Grimal et al [ 29 ] found a steadily increase of median liver stiffness in rats with NASH, measured by SWE, with exacerbation of steatosis grade.…”

Mechanical properties of human hepatic tissues to develop liver-mimicking phantoms for medical applications

“…The frequency response in the KVFD model undergoes a monotonically increase dissimilar to that in the SLS model, attaining a plateau (Glińska-Suchocka et al 2017 ; Pi et al 2021 ). In addition, the measured velocity during the propagation of shear waves across the liver at distinct values ranging from 40 Hz to 14 MHz indicates the monotonical increase of shear velocity with frequency (Glińska-Suchocka et al 2017 ; Pi et al 2021 ). Concluding from the dynamic testing on tissues of the canine liver, the KVFD model exhibited a good fit with the experimental data compared to other models, such as the KV model (Yeh et al 2015 ).…”

“…The model has to satisfy both the ex vivo dynamic mechanical analysis (DMA) experiment at low frequency (1–41 Hz) and the in vivo shear wave elastography (SWE) experiment at high frequency (160–380 Hz) (Pellot-Barakat et al 2016 ). Table 5 summarizes the fitness profile for each of the three models to the shear wave velocity (Lin et al 2017 ; Pi et al 2021 ). The tabulated results reveal that the best model characterizing the rats’ mechanical properties at every steatosis stage is the Voigt model with a determination coefficient ( R 2 ) near 1.…”

“…Realistic mechanical properties can help to advance radiation therapy techniques, for example, using magnetic resonance imaging (MRI) or four-dimensional computed tomography (4D CT) to assess an organ displacement during the response to the respiratory motion (Pi et al 2021 ). In addition, the prior knowledge of the liver’s mechanical behavior will enhance the predictive abilities of algorithms for tumor localization (Tian et al 2015 ).…”