2D shear wave elastography for the assessment of quadriceps entheses-a methodological study

Area of Science:

• Musculoskeletal imaging
• Rheumatology
• Medical ultrasonography

Background:

• 2-dimensional shear wave elastography (SWE) is a non-invasive ultrasound technique used to assess tissue stiffness.
• Standardized protocols are essential for reproducible elasticity measurements in normal entheses.
• Variability in SWE measurements can arise from confounding factors such as coupling gel thickness, patient positioning, and acquisition parameters.

Purpose of the Study:

• To establish a reliable scanning protocol for 2-dimensional SWE on normal quadriceps entheses.
• To investigate confounding factors influencing measured elasticity and identify optimal parameters for reproducible results.
• To minimize variability in SWE measurements of entheseal stiffness.

Main Methods:

• 30 normal quadriceps entheses were scanned using 2-dimensional SWE.
• The study systematically varied coupling gel thickness, knee position (flexion vs. extension), region of interest (ROI) size (2.0 mm vs. 4.0 mm diameter), and scanning plane (longitudinal vs. transverse).
• Stiffness (median shear wave velocity - SWV) and coefficient of variation were compared across different parameters.

Main Results:

• No significant difference in median SWV was found with varying coupling gel thickness.
• Higher median SWV (increased stiffness) was observed with knee flexion, larger ROI size (4.0 mm), and transverse scanning plane.
• Lower coefficient of variation was achieved with a 2.0 mm ROI, longitudinal plane, extended knee, and thicker gel (2.5 cm).
• Strong correlation was noted between SWV and the angle between shear wave and muscle fiber direction (ρ=0.8, p<0.001).
• Interobserver reliability for the proposed protocol was good (Intraclass Correlation Coefficient = 0.763).

Conclusions:

• The optimal scanning protocol for reliable SWE imaging of healthy quadriceps entheses involves a supine position with the knee extended.
• Using a 2.0 mm diameter region of interest and acquiring images in the longitudinal plane with a thicker layer of coupling gel is recommended.
• This standardized approach minimizes variability and enhances the reproducibility of elasticity measurements in entheses.