Reliability of liver stiffness measurements using shear wave elastography: impact of skin-to-capsule distance and subcutaneous tissue structure

Purpose: Shear wave velocity (Vs) measurements can be unstable in individuals with obesity or with a skin-capsule distance (SCD) of ≥ 20 mm. However, instability of Vs has also been observed in cases where SCD is not markedly increased; therefore, the present study aimed to investigate the factors contributing to reduced VsN (net amount of effective shear wave velocity), an index that reflects the reliability of individual Vs measurements. Methods: In total, 317 individuals who underwent community-based health screening were included in this study. We investigated the relationship between VsN and physical findings, laboratory data, SCD, and structure of the SCD (single vs. multilayered) to identify factors associated with decreased VsN. Results: Multiple regression analysis revealed that body fat percentage (β = − 0.135, p = 0.011), SCD (β = − 0.347, p < 0.0001), and the structure of the SC region (β = − 0.295, p < 0.0001) were independently associated with decreased VsN. In cases where the SCD exceeded 20 mm, the VsN within the SCD was significantly lower in the multilayer structural type [52 (28–75)] than in the single-layer structural type [95 (77–99)] (p = 0.004). Furthermore, even when the SCD was 20 mm or less, the VsN within the SCD was significantly lower in the multilayer structure type [80 (68–89)] than in the single-layer structure type [99 (92–100)] (p < 0.0001). Conclusion: The results show that, in addition to SCD thickness, its internal structure reduces the VsN and contributes to Vs measurement instability.