This study concerns the development and preliminary experimental verification of a topological sensitivity–based platform for the material characterization of tissue anomalies exposed by vibroacoustography-type imaging techniques. Vibroacoustography (VA) is a high-resolution imaging method that has been applied to the detection of pathological changes in soft tissues. Although the data provided by this method is related to the mechanical properties of tissue, the viscoelastic parameters of the object cannot be estimated by this imaging method itself. Topological sensitivity (TS) method is a data processing methodology that can be used to estimate the viscoelastic parameters of an object from vibration data. In this study, the concept of topological sensitivity is applied to interpret the vibroacoustography measurements for the purpose of lesion characterization. In the proposed approach, the topological sensitivity function, which signifies the variation of a given cost functional when an infinitesimal inclusion with trial material parameters is placed at the location of a point force, is formulated in terms of the adjoint field. The effectiveness of the resulting formula as a material indicator for lesion characterization is demonstrated by estimating the relative elastic parameters of a well-controlled neoprene sphere embedded in a tissue-mimicking phantom specimen.
h i g h l i g h t s• A general 3D contact smoothing method using radial point interpolation is proposed. • The method constructs local contact surfaces with polynomial and radial bases.• The constructed surface is smooth and passes exactly through the surface nodes.• The method shows good approximation in both coordinates and normal vector.• It can effectively reduce contact force oscillation and solve the chatter problem.
a b s t r a c tThis paper presents a general 3D contact smoothing method based on the meshfree radial point interpolation method to improve the numerical simulation of contact problems. In particular, a locally smooth contact surface is constructed from the scattered surface nodes by point interpolation using the combination of polynomial and radial bases. With such bases, this method reproduces smooth surfaces even for coarse meshes and the constructed surface passes exactly through the surface nodes. Results for contact problems involving deformable bodies are included to demonstrate its advantages.
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