Optimization and Reliability Assessment of Ultrasound Shear Wave Elastography of the Rectus Femoris: A Methodological...

To evaluate effects of various sections, operational methods, and measurement techniques of shear wave elastography (SWE) on the assessment of rectus femoris stiffness.

This study included 43 healthy volunteers who underwent rectus femoris SWE using different sections (cross-sectional and longitudinal), operation methods (hand-held, thick coating couplant, and acoustic pad), and measurement methods (circular, multipoint, and tracing). Two sonographers evaluated the inter-observer and intra-observer consistency of SWE longitudinal-section measurements for the first 20 healthy volunteers.

The longitudinal section had lower median values of shear wave velocity (SWV) and shear modulus (1.7 m/s vs. 1.9 m/s, 9.3 kPa vs. 11.4 kPa), whereas the transverse section exhibited higher coefficients of variation (17.14% vs. 10.94%, 33.80% vs. 27.70%). Excellent inter-observer agreement on SWV and shear modulus was observed for the longitudinal section (ICC: 0.97, 0.96, 95% CI: 0.883-0.991, 0.800-0.988; p < 0.001). The intra-observer agreement for SWV was substantial (ICC = 0.64) while that for the shear modulus was moderate (ICC = 0.23). Median SWVs of the handheld, thick-coated couplant, and acoustic-pad methods decreased in order (1.9 m/s, 1.7 m/s, 1.6 m/s, respectively). The handheld method had the lowest coefficient of variation (CV) compared to the other two methods (10.94%, 13.87%, and 14.56%, respectively). No statistically significant differences were observed in SWV measurements and CV between circle, multipoint, and tracing methods (p > 0.05).

The longitudinal section and handheld method offered enhanced stability when measuring muscle stiffness; shear SWV exhibited superior consistency compared to shear modulus. The region-of-interest tracing method was straightforward and had an extensive measurement range.