Impact of Probe Pressure and Patient Position on QUS Accuracy for Hepatic Steatosis

Overview

This study evaluated how probe pressure and patient positioning affect the diagnostic accuracy of ultrasound-guided attenuation parameter (UGAP) for detecting hepatic steatosis in men and women. Results demonstrated that both increased probe pressure and body position influence UGAP measurements, with sex-specific differences in diagnostic thresholds.

Background

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects up to 38% of populations in some regions and is linked to increased mortality. Hepatic steatosis is essential for MASLD diagnosis, traditionally assessed by liver biopsy or MRI proton density fat fraction (PDFF). Conventional ultrasound is widely used but limited by qualitative grading and low sensitivity in mild steatosis. Quantitative ultrasound (QUS) attenuation imaging, such as UGAP, offers a non-invasive method to quantify liver fat but may be influenced by probe pressure, patient position, and sex differences in fat distribution.

Data Highlights

Key Findings

• UGAP measurements are affected by probe pressure, with increased pressure (30 N) altering attenuation values compared to normal pressure (4 N).
• Patient body position (supine vs. 30° left decubitus) influences UGAP diagnostic accuracy for hepatic steatosis.
• Sex differences exist in fat distribution, necessitating potentially different UGAP thresholds for men and women to detect ≥5% liver fat.
• UGAP demonstrated reliable reproducibility with repeated measurements performed 1–3 months apart under standardized conditions.
• Using a quality map and strict criteria (IQR/median ratio <30%) ensures reliable UGAP measurements.

Clinical Implications

Clinicians should consider probe pressure and patient positioning when performing UGAP to assess hepatic steatosis, as these factors impact measurement accuracy. Additionally, sex-specific diagnostic thresholds may improve detection sensitivity and specificity. Standardizing measurement protocols including probe force and body position can enhance the reliability of QUS in clinical practice.

Conclusion

Probe pressure and patient position significantly influence the diagnostic precision of UGAP for hepatic steatosis, with sex-specific considerations important for accurate interpretation. Standardized measurement techniques are essential to optimize QUS utility in MASLD diagnosis.

References

1. Global MASLD prevalence and mortality risk [1,2]
2. MRI-PDFF as reference standard for liver fat quantification [9-12]
3. Limitations of conventional ultrasound in MASLD diagnosis [13-19]
4. QUS attenuation imaging and UGAP technology [20-34]