Confounding factors in ultrasound liver elastography. Part 1. General provisions and methodological errors

Abstract

The aim of the study is a systematic analysis of literature data on the effect of methodological factors, artifacts, as well as external influences and features of the state of the organism on the results of ultrasonic elastography of the liver. Two-dimensional shear wave elastography is a highly accurate method for assessing the degree of liver fibrosis, provided that the study methodology is strictly followed, however, the influence of measurement disturbances should be taken into account. Confounding factors lead to an erroneous change in the liver stiffness from insignificant, within 5-10%, to considerable, catastrophically distorting the assessment of the degree of liver fibrosis. Confounding factors include three main groups: 1) methodologically determined, as well as physical artifacts and equipment features; 2) internal (endogenous) and 3) external (exogenous). The first group of confounding factors includes: non-observance by the operator of the standard rules for manipulating the probe, positional features of the patient, insufficient size of the window area of the area of interest, incorrect location of the area of interest, lack of adequate breath holding by the patient or the performing of his/her movements, insufficient number of measurements, large spread of recorded values, transmission pulsations from the heart and large vessels, features of the equipment used, physical essence of the elastographic method and artifacts.

Keywords

• ultrasound
• shear wave elastography
• liver fibrosis
• stiffness
• young’s modulus
• liver