What is the role of measuring shear wave dispersion using shear wave elastography in pancreatic parenchyma?

Abstract

Shear wave elastography (SWE) using transabdominal ultrasonography (US) is widely used for diagnosis of tissue stiffness. Ultrasound shear wave dispersion (SWD) enables evaluation of tissue viscosity using SWE. The objective of this study was to investigate the reliability and clinical significance of SWD in pancreatic screening. SWE and SWD were measured in 76 patients examined by US in pancreatic screenings performed between November 2017 and November 2018. The median pancreatic elastic modulus (PEM) and dispersion slope were obtained from at least five measurements. The reproducibility of these values and their correlations with patient characteristics, pancreatic echogenicity, and the pancreas-to-spleen attenuation ratio (P/S) on plain CT, which is associated with fatty change in pancreatic parenchyma, were investigated retrospectively. The median PEM and dispersion slope were 7.4kPa and 15.7 (m/sec)/kHz, respectively, and both values had high intraclass correlation coefficients, showing high reproducibility (ρ = 0.869 and ρ = 0.867, respectively). The interquartile range/median value of PEM and dispersion slope were 0.36 and 0.28, respectively. PEM had a positive correlation with age (rs = 0.348, p = 0.002), and dispersion slope was positively correlated with age (rs = 0.278, p = 0.016) and BMI (rs = 0.397, p < 0.001). The hyperechoic pancreas had significantly higher PEM (6.6 vs. 7.8kPa, p = 0.037) and dispersion slope (13.2 vs. 16.3 (m/sec)/kHz, p < 0.001). On plain CT performed in 50 patients, the P/S was not correlated with PEM (rs = -0.180, p = 0.221), but was inversely correlated with dispersion slope (rs = -0.338, p = 0.019). Measurement of SWD in pancreatic screening was highly reproducible and may permit objective evaluation of fatty change of the pancreas.