Tomographic imaging of shear modulus elasticity of biological tissue based on ultrasonic measurement of internal displacement

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Palpation has been the clinical diagnostic modality to detect the changes in soft tissue elasticity, because the elasticity is usually related to some abnormal, pathological process. The goal of this study is to characterize tissue elasticity based on ultrasonic measurement of internal tissue deformation and displacement when the primary cardiac pulsation or the external mechanical force is applied to the soft tissue. A variational formulation is presented for the determination of the elasticity parameter of an isotropic, inhomogeneous, incompressible biological soft tissue, subject to external mechanical forces. Given a knowledge of the displacements throughout the tissue. A finite-element based model for static deformation is proposed for solving the distribution of the relative shear or Young's modulus of the tissue. The feasibility of the proposed method is demonstrated using the simulated deformation data of the simple three-dimensional inclusion problem. The results show that the … More relative shear modulus may be reconstructed from the displacement data measured locally in the region of interest within an isotropic, incompressible medium, and that the relative shear modulus can be recovered to some degree of accuracy from only 2-dimensional displacement data.Experiments on tissue mimicking phantoms were done. Mesurements are performed using real-time ultrasound and the sequences of RF echo signal returned from tissue ware digitized to estimate local tissue displacement. The 2-dimensional distribution of internal displacement was estimated using the spatio-temporal derivative of RF echo envelope signals, from which components of internal strain tensor were computed. Experimental results indicate that 2-dimensional fields of components of displacement can be estimated with the spatial resolution of 5mmx5mm. The distribution of the relative shear modulus based on displacement images was reconstructed. The elasticity of soft tissue can be characterized as the relative shear modulus computed from the local displacement data observed in the received RF echo signals. Less