Increased Mechanical Index Improves Shear Wave Elastography: Pilot Study of Signal Enhancement

Objective

Monitoring liver stiffness is essential for managing chronic liver disease, which poses a major public health challenge. Shear wave elastography (SWE), a non-invasive ultrasound-based technique, is commonly used to quantify liver stiffness. However, its performance can be compromised in individuals with higher body mass indices (BMIs) due to increased ultrasound absorption and distortion. Increasing the intensity of the ultrasound push beam could potentially improve signal quality, but regulatory limits currently restrict this due to safety concerns. This pilot study investigated the efficacy of increasing the push pulse mechanical index (MI) from a conventional value of 1.4 to 2.5 toward improving signal quality, and reducing measurement variability and failure rates.

Methods

Healthy volunteers ($N=$22) stratified by BMI underwent SWE with conventional and increased MI push pulses. The resulting data were processed with conventional SWE algorithms, and the signal and measurement quality of the results were analyzed.

Results

We found that the higher MI improved the signal-to-noise ratio by 4.6 dB ($p<$10^-4, 95% confidence interval: 3.4–5.8 dB) and reduced the measurement's coefficient of variation by 13% ($p<$10^-4, 95% confidence interval: 5.8%–20.3%), enhancing the success rate of SWE examinations, especially for subjects with a BMI over 30. Liver function tests before and after the SWE examinations showed no signs of bioeffects or harm based on serum biomarkers.

Conclusion

These results suggest that increasing the push pulse MI to 2.5 improves the diagnostic utility of SWE, particularly for individuals with a higher BMI, without introducing significant additional risk. This approach could further enhance SWE's vital role in the monitoring of chronic liver disease at a population scale.