Tissue quantification with acoustic radiation force impulse imaging: Measurement repeatability and normal values in the healthy liver.

OBJECTIVE The purpose of this study was to describe the most reliable measurement procedure for acoustic radiation force impulse technology and to define the normal wave velocity values in a healthy liver. SUBJECTS AND METHODS Twenty healthy volunteers underwent acoustic radiation force impulse imaging tissue quantification and were enrolled in this prospective study. All patients were examined by two independent operators at the same time. Twenty-four measurements per subject were obtained. Intraoperator and interoperator evaluations were performed. Statistical comparison of all mean data was performed with Student's t test. A value of p < 0.05 was considered significant. A comparative analysis was performed, and interclass correlation coefficients were calculated. RESULTS The operators obtained 960 measurements. A statistically significant difference was found between the mean shear wave velocity values obtained by one operator deep in the right lobe of the liver and the values obtained on the surface of the right lobe (1.56 vs 1.90 m/s) and between the mean values obtained deep in the right lobe and those obtained deep in the left lobe (1.56 vs 1.84 m/s). The other operator had similar results. The distribution of all mean values obtained by both operators deep in the right hepatic lobe exhibited less dispersion (95% CI, 1.391-1.725) than those obtained on the surface (95% CI, 1.664-2.136). In 77.5% of cases, the shear wave speeds were between 1 and 2 m/s. No statistically significant difference was found in the comparisons performed on the right hepatic lobe by the two operators. The interclass correlation coefficient calculated for measurements deep in the right lobe was 0.87 (p < 0.0001). CONCLUSION Acoustic radiation force impulse imaging quantification of hepatic tissue is more reproducible when applied to the deeper portion of the right lobe of the liver.