Real-time two-dimensional Shear-wave elastography for liver stiffness in children: Interobserver variation and effect of breathing technique

Abstract

Objectives: To evaluate interobserver variation and to assess the effect of the breathing technique on liver stiffness (LS) measurement using real-time two-dimensional shear-wave elastography (2D-SWE) in children.

Methods: Patients who underwent real-time 2D-SWE by two operators (group 1) and patients who underwent real-time 2D-SWE by one operator using the free-breathing and breath-holding techniques (group 2) were included. In group 1, interobserver agreement was assessed using the intraclass correlation coefficient (ICC) and the 95% limits-of-agreement was analyzed to evaluate the maximum change in the LS values based on Bland-Altman analysis. In group 2, the Bland-Altman plot and the paired t-test were used to determine the effect of breathing technique on LS measurement.

Results: The interobserver agreement of the LS measurement in group 1 (n=63) was excellent (ICC, 0.953), and the 95% limits-of-agreement was 31.8% of the mean LS values. In group 2 (n=45), the free-breathing technique revealed systematically lower LS with a mean difference of -11.1% of the mean LS values, compared to the breath-holding technique (P=0.016).

Conclusion: LS measurement assessed by real-time 2D-SWE in children showed excellent interobserver agreement. Changes in LS values less than 31.8% of the mean LS values may represent the measurement error. The free-breathing technique showed lower LS values, compared to the breath-holding technique.

Keywords: Children; Elastography; Liver; Reproducibility; Ultrasound.