Date Published: January 20, 2017
Publisher: Public Library of Science
Author(s): Jingxin Zhao, Fei Zhai, Jun Cheng, Qiong He, Jianwen Luo, Xueping Yang, Jinhua Shao, Huichun Xing, Jee-Fu Huang.
Transient elastography quantifies the propagation of a mechanically generated shear wave within a soft tissue, which can be used to characterize the elasticity and viscosity parameters of the tissue. The aim of our study was to combine numerical simulation and clinical assessment to define a viscoelastic index of liver tissue to improve the quality of early diagnosis of liver fibrosis. This is clinically relevant, as early fibrosis is reversible. We developed an idealized two-dimensional axisymmetric finite element model of the liver to evaluate the effects of different viscoelastic values on the propagation characteristics of the shear wave. The diagnostic value of the identified viscoelastic index was verified against the clinical data of 99 patients who had undergone biopsy and routine blood tests for staging of liver disease resulting from chronic hepatitis B infection. Liver stiffness measurement (LSM) and the shear wave attenuation fitting coefficient (AFC) were calculated from the ultrasound data obtained by performing transient elastography. Receiver operating curve analysis was used to evaluate the reliability and diagnostic accuracy of LSM and AFC. Compared to LSM, the AFC provided a higher diagnostic accuracy to differentiate early stages of liver fibrosis, namely F1 and F2 stages, with an overall specificity of 81.48%, sensitivity of 83.33% and diagnostic accuracy of 81.82%. AFC was influenced by the level of LSM, ALT. However, there are no correlation between AFC and Age, BMI, TBIL or DBIL. Quantification of the viscoelasticity of liver tissue provides reliable measurement to identify and differentiate early stages of liver fibrosis.
Liver fibrosis is generally caused by an excess accumulation of extracellular matrix proteins and occurs in most types of chronic liver diseases. The etiology of liver fibrosis is multifactorial in nature, with viral infection, alcohol overuse, and nonalcoholic steatohepatitis being common causes . Liver fibrosis is an important health issue as it generally leads to liver cirrhosis and even cancer and, therefore, it is associated with serious long-term consequences in terms of patient morbidity and mortality .
Liver disease is prevalent in China and its diagnosis and treatment is a relevant clinical issue. Chronic liver diseases usually develop gradually and are associated with a process of liver fibrosis. As the early stage of liver fibrosis can be reversed with treatment, there has been increasing emphasis placed on developing a diagnostic technique to accurately identify liver disease in its early stages. Although elastography has emerged in recent years as a diagnostic technique for liver disease that is superior to conventional imaging techniques, without the risks associated with biopsy, its application remains limited for reliable identification of early stage liver disease, such as the differentiation of F1 and F2 stages of liver disease. The AFC that we developed in this study, based on vibration amplitude attenuation, provides a more accurate diagnosis of early stage liver fibrosis than LSM.