Mapping viscoelastic properties by multi-line (ML) acoustic radiation force

Abstract

In these days ultrasound studies of non-invasive diagnostic methods using the elastic property of tissue have showed very promising results. Biological soft tissues are viscoelastic in nature; therefore several recent studies have shown the feasibility of shear wave dispersion in order to express viscosity which is considered to be valid for early diagnoses. Shear wave Dispersion Ultrasound Vibrometry (SDUV) has been conducted under ex vivo and in vivo conditions, which could estimate the value of shear elasticity and viscosity from a 40 x 40 mm 2 area. In this study, our proposed Multi-line (ML) acoustic radiation force method could map shear elasticity and viscosity at 0.2 x 0.2 mm 2 pixel in 25.6 mm width and 29.6 mm depth area. ML uses seven focus points in depth to create much planar shear wave than ever, and twenty pushing line to obtain data such a broader area than ever. These sequences contribute to express precise values of shear elasticity and viscosity at each pixel. A 10% gelatin phantom with a 10% gelatin and 1% xanthan gum mixture inclusion was prepared for ML experiment, and one homogenous phantom made of the same concentrations as the background of ML experiments was for ML and SDUV experiments three times to validate. The ML measurement resulted μ 1 = 1.129±0.118 kPa, μ 2 = 0.893±0.090 Pa･s in the 10% gelatin background; their corresponding SDUV measurement were μ 1 = 1.250±0.129 kPa, μ 2 = 0.833±0.098 Pa･s in 10% gelatin phantom. Though further evaluations such as frequency and rheological model are required, the results could show the effectiveness of this proposed method in mapping viscoelasticity and the feasibility of in vivo and ex vivo experiments.