Interconversion of elasticity measurements between two-dimensional shear wave elastography and transient elastography

Aims: To enable comparison and interconversion of elasticity measurements between two-dimensional (2D) shear wave elastography (SWE) and transient elastography (TE). Materials and methods: Elasticities of three phantoms were measured by 2D SWE (supersonic shear imaging) using four probes and TE using two probes. We performed regression analyses to evaluate correlation between the measurements and phantom elasticities, and make converting equations. In pediatric biliary atresia patients who had stiffness measurements by both 2D SWE and TE within 1-year interval, TE measurements were retrospectively converted into correlating 2D SWE values. We compared the calculated values with 2D SWE measurements by intraclass correlation coefficient. Results: Measurements in phantoms varied according to elastography method and probe selection. However, the measurement by both 2D SWE (R², 0.974-0.985; p<0.001) and TE (R², 0.996-0.999; p<0.001) showed significant linear correlation with phantom elasticity in all probe settings. From 67 biliary atresia patients (age, 2 months-20 years), agreements between the measured and calculated values were excellent in all 88 examinations within 1-year interval (ρ=0.828; p<0.001) and in 63 examinations within 2-month interval (ρ=0.863, p<0.001). Conclusions: The equations enabled interconversion of elasticity values among different probes of 2D SWE and TE and provided reliable estimation of elasticity values for different probe settings in biliary atresia patients.