Does Operator Experience and the Q‐Box Diameter Affect the Repeatability of Liver Stiffness Measurements Obtained by 2‐Dimensional Shear Wave Elastography?

Objectives The purpose of this research was to evaluate whether operator experience and the quantitative analysis system (Q-Box; SuperSonic Imagine, Aix-en-Provence, France) diameter affect the repeatability of liver stiffness measurements. Methods We enrolled 417 outpatients. All measurements were performed by 2 operators, including an expert and a novice. Each patient was continuously measured 3 times by the 2 operators. The Q-Box diameter was adjusted to 10, 20, and 30 mm each time, and the mean elasticity values were recorded. Intraobserver repeatability was evaluated by the intraclass correlation coefficient (ICC). Interobserver repeatability was evaluated by the ICC, coefficient of variation (CV), and Bland-Altman plots. Results The study group included 241 male and 176 female patients. The expert operator had higher ICCs than the novice operator at each Q-Box diameter. The overall interobserver agreement was excellent, and the results showed that compared to other groups, the ICC was the lowest and the CV was the largest for the 30-mm-diameter group. The ICC and CV values were similar between the 10- and 20 mm-diameter groups. The Bland-Altman plots showed that the mean difference was -0.2 kPa for the 10-, 20-, and 30 mm-diameter groups. However, the limits of agreement were the largest in the 30-mm-diameter group and were similar between the 10- and 20-mm-diameter groups. Conclusions The repeatability of liver stiffness measurements is affected not only by experience but also by the Q-Box diameter.