Liver Elastography: Basic Principles, Evaluation Technique, and Confounding Factors

Ultrasound-based elastography techniques have received considerable attention in the last years for the noninvasive assessment of tissue mechanical properties. These techniques have the advantage of detecting tissue elasticity changes occurring in various pathological conditions and are able to provide qualitative and quantitative information that serves diagnostic and prognostic purposes. For liver applications and especially for the noninvasive assessment of liver fibrosis, ultrasound-based elastography has shown promising results. Several ultrasound elastography techniques using different excitation methods have been developed. In general, these techniques are classified into strain elastography, which is a semi-quantitative method that uses internal or external compression for tissue stimulation, and shear wave elastography, which measures the ultrasound-generated shear wave speed at different locations in the tissue. All liver elastography techniques have a standardized examination technique, with the patient in a supine position, while the measurements are performed through the right liver lobe. There are also some confounding factors that need to be taken into account when performing liver elastography such as a higher level of aminotransferases, infiltrative liver disease, liver congestion, cholestasis. This chapter briefly introduces the basic principles of liver elastography and discusses some important clinical aspects of elastography, such as the examination technique and the limitations