Precompression Artifact in Elastography: How Probe Pressure Overestimates SWE and Strain

Mechanism of Precompression Artifact

Probe pressure causes compression of superficial tissues due to the nonlinear stress-strain characteristics of the tissue. According to EFSUMB (Update 2017, liver), this leads to artifactually high shear wave speed; however, for the liver, the artifact is usually not a problem as it occurs only near the surface.

In non-hepatic applications (EFSUMB Update 2018, non-hepatic), probe precompression increases the stiffness of all tissues and should be eliminated as it distorts the results of both SWE and strain elastography.

Controlling Precompression Using Normal Adipose Tissue

According to EFSUMB (non-hepatic, 2018), normal adipose tissue has E-mean values in the range of 5–10 kPa (in SWE, if the scale is set from 0 to 180). If the color changes according to these values, precompression should be adjusted. The color scale can be changed, which must be considered during interpretation.

Quality Indicators and Correct Compression

According to Diagnostic Imaging: Breast (Berg, Leung, 2019), quality indicators for SWE and strain include the associated color bar, color overlay, or numerical value, ensuring correct compression. For the breast, the maximum scale is often set at 7.7 m/s (180 kPa).

Data provided by Diagnostic Imaging: Breast (2019) for comparing SWE and strain in characterizing breast lesions.

Practical Recommendations

To minimize the precompression artifact, avoid excessive probe pressure, focus on the E-values of normal adipose tissue, and adjust compression if the color pattern deviates from the expected range (5–10 kPa, SWE). Using a color scale, overlay, or numerical indicator helps confirm the correctness of compression.