title: Quantification of liver viscoelasticity with acoustic radiation force: a study of hepatic fibrosis in a rat model.
abstract: Ultrasound elastography, based on shear wave propagation, enables the quantitative and non-invasive assessment of liver mechanical properties such as stiffness and has been found to be feasible for and useful in the diagnosis of hepatic fibrosis. Most ultrasound elastographic methods use a purely elastic model to describe liver mechanical properties. However, to describe tissue that is dispersive and to obtain an accurate measure of tissue elasticity, the viscoelasticity of the tissue should be examined. The objective of this study was to investigate the shear viscoelastic characteristics, as measured by ultrasound elastography, of liver fibrosis in a rat model and to evaluate the diagnostic accuracy of viscoelasticity for staging liver fibrosis. Liver fibrosis was induced in 37 rats using carbon tetrachloride (CCl4); 6 rats served as controls. Liver viscoelasticity was measured in vitro using shear waves induced by acoustic radiation force. The measured mean values of liver elasticity and viscosity ranged from 0.84 to 3.45 kPa and from 1.12 to 2.06 Pa·s for fibrosis stages F0-F4, respectively. Spearman correlation coefficients indicated that stage of fibrosis was well correlated with elasticity (0.88) and moderately correlated with viscosity (0.66). The areas under receiver operating characteristic curves were 0.97 (≥F2), 0.91 (≥F3) and 1.00 (F4) for elasticity and 0.91 (≥F2), 0.79 (≥F3) and 0.74 (F4) for viscosity, respectively. The results confirmed that shear wave velocity was dispersive in frequency, suggesting a viscoelastic model to describe liver fibrosis. The study finds that although viscosity is not as good as elasticity for staging fibrosis, it is important to consider viscosity to make an accurate estimation of elasticity; it may also provide other mechanical insights into liver tissues.
authors.affiliation: School of Medicine, Shenzhen University, Shenzhen, China; National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen, China; Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, Shenzhen, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Shen
authors.forename: Yi
authors.initials: Y
authors.lastname: Zheng
authors.forename: Haoming
authors.initials: H
authors.lastname: Lin
authors.forename: Yanrong
authors.initials: Y
authors.lastname: Guo
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhu
authors.forename: Xinyu
authors.initials: X
authors.lastname: Zhang
authors.forename: Tianfu
authors.initials: T
authors.lastname: Wang
authors.forename: Siping
authors.initials: S
authors.lastname: Chen
mesh_terms: D000818:Animals; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005240:Feasibility Studies; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008103:Liver Cirrhosis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014783:Viscosity
keywords: Acoustic radiation force; Liver fibrosis; Shear wave; Viscoelasticity