The Experimental Study By Ultrasound Tissue Mimicking Phantoms Based On The Shear Wave Elastography

Objective To analyze the correlation between the relevant physical parameters and the elastic modulus of shear wave elastography(SWE) by making ultrasound tissue mimicking phantoms(including nodule phantoms and background phantoms). To evaluate the change of elastic modulus among different conditions. To discuss what factors may caused and affect the SWE “window” phenomenon.Methods Prepared nodule phantoms with different densities and viscosities applicating the gelatin as the main ingredients, and embedded in the background phantoms, and then measured the maximum elastic modulus(Emax). Using factorial designed to evaluate the factors(such as density, viscosity, depth, and the hardness of background) relative to Emax of nodule phantoms. Applying the binary Logistic regression to analysis the factors(including density, viscosity, diameter, depth, and the hardness of background) relative to the SWE “window” phenomenon.Results With increasing gelain ratio in nodule phantoms from number 1 to 20, the density and viscosity increased.Main effects of the nodule phantoms number(corresponding density and viscosity), depth, and the hardness of background had a difference on the Emax of nodule phantoms, which existed interactive effects(P<0.05). From number 1 to 20, the Emax of nodule phantoms had significant difference(P<0.05). With the density and viscosity increased, the Emax also increased, and the Linear and Logarithmic were the best fit model for the Emax. The Emax of nodule phantoms between two depth level(<3.0cm and ?3.0cm) had significant difference(P<0.05). When the position is shallow, and the Emax of nodule phantoms were higher. The Emax of nodule phantoms between three kinds of the hardness of background(soft, medium, and hard) had significant difference(P<0.05). In hard-background phantoms, the Emax of nodule phantoms were maximum, and the second were medium-background phantoms, and the Emax of nodule phantoms embedded in soft-background phantoms were minimal.The nodule phantoms number(corresponding density and viscosity), nodule phantoms diameter and depth were independent risk factors of the SWE “window” phenomenon(P<0.05), and the corresponding odds ratio(OR) were 23.846, 0.093, and 0.003. Compare with the non-“window” group, the “window” group had lower density and viscosity, bigger diameter, and deeper position. Fixing any two independent risk factors above at the same time according to the OR, and reducing the density and viscosity, or increasing the diameter and depth of nodule phantoms, which could increase the possibility of the SWE “window” phenomenon.Conclusions By changing the gelain ratio of ultrasound tissue mimicking phantoms could change their density and viscosity flexible. The density and viscosity could be increased through adding gelain. Nodule phantoms embedded in the background phantoms, which could simulate a pathologic state of nodule existing in a normal tissue.The density and viscosity of nodule phantoms, depth, and the hardness of background had an effect on the Emax, and all of them existed interactive effects. Therefore, combined the three factors to synthetically analysis the results of SWE is necessary.The density and viscosity of nodule phantoms, nodule phantoms diameter, and depth had an effect on the SWE “window” phenomenon. The possibility of the SWE “window” phenomenon could be inreased if the density and viscosity of nodule phantoms are reduced or the diameter and depth are increased.