Liver Fibrosis Assessment by Point Shear-Wave Elastography Techniques

Abstract

Point shear-wave elastographic (pSWE) techniques use acoustic radiation force impulse (ARFI) to stimulate the liver tissue and to generate shear waves that propagate into the liver. The shear-wave velocity (SWV) increases with the severity of fibrosis. The first type of pSWE was Virtual Touch Quantification (VTQ) developed by Siemens, followed by ElastPQ by Philips, and nowadays pSWE is available on other systems (Hitachi, Esaote, Samsung). To evaluate liver fibrosis by pSWE, ten valid measurements are performed in the right liver lobe; a median value is calculated, with the results expressed in meters/second or in kilopascals (kPa) (if the operator chooses). VTQ is a reproducible method, the intraclass correlation coefficient (ICC) for inter-and intraobserver measurements ranging from 0.81 to 0.87. Confounding factors for VTQ are non-fasting conditions, elevated aminotransferases, congestive heart failure, and extrahepatic cholestasis. In patients with chronic hepatopathies, the AUROCs for predicting significant fibrosis range between 0.75 and 0.85 and for predicting cirrhosis between 0.85 and 0.95. There were promising results regarding the value of VTQ to predict liver cirrhosis complications, especially portal hypertension. ElastPQ is a newly developed point shearwave elastographic method (from Philips). Only few data were published but with promising results.

Diagnostic Performance of Point Shear Wave Elastography (pSWE) Using Acoustic Radiation Force Impulse (ARFI) Technology in Mesenteric Masses: A Feasibility Study

“…In two-dimensional (2D)-SWE, body tissues are stimulated at different points, generating propagating shear waves, which are monitored in real time at different locations within the image, thus generating a quantitative elastogram in the form of a “topographic” colored map correlating to a scale of different elastic measurements in m/s or kilopascals [ 32 ]. In point shear wave elastography (pSWE), such as acoustic radiation force impulse (ARFI) pSWE, the resulting shear waves propagate in a direction perpendicular to the axial stimulating acoustic beam, and the speed of propagation of these shear waves is measured within a region of interest (ROI) by estimating the time needed to travel from the border near to the stimulus to the border away from the stimulus [ 33 ]. Both pSWE and 2D-SWE have excellent performance in assessing liver fibrosis and cirrhosis [ 34 , 35 , 36 ], with good reproducibility [ 34 , 37 ], and both modalities perform similarly well in differentiating malignant and benign lesions [ 38 , 39 , 40 ].…”