Validation of intra- and interobserver reproducibility of shearwave elastography: Phantom study

To assess intra- and interobserver reproducibility of quantitative ultrasound (US) elastography for breast masses using shearwave elastography (SWE).

The US elastography phantom was used. This training phantom contained 12 masses with dimensions from 6 to 11mm and varying B-mode (hypo- iso- and hyperechoic) characteristics and viscoelastic properties varying from about 50 to 250kPa. Four attending radiologists participated as operators and used Supersonic Imaging 15-4 MHz array to acquire images. In each session, B-mode US features were assessed once and US elastography values were assessed twice in a consecutive and distinct manner. A total of three identical sessions of data acquisition were performed at 2-week intervals. For categorical variables such as BI-RADS features of mass on B-mode image and qualitative SWE features, kappa (k) values were calculated by the generalized linear mixed model. For continuous variables, kPa, and ratio, intraclass correlation coefficients (ICCs) were calculated.

Interobserver agreement for SWE image similarity was moderate (k=0.57). With respect to quantitative SWE values, intraobserver ICCs were 0.65, 0.77, 0.92, and 0.91 for maximum elasticity; 0.70, 0.83, 0.94, and 0.94 for mean elasticity; and 0.67, 0.83, 0.92, and 0.92 for elasticity ratio for operators 1, 2, 3, and 4, respectively. Interobserver reproducibility showed good agreement with ICC values of 0.77 for maximum elasticity, 0.82 for mean elasticity, and 0.79 for elasticity ratio.

Quantitative US elastography for breast masses was highly reproducible with good agreement across operators. With respect to intraobserver reproducibility, ICC values varied but three out of four operators showed good agreement.