Measurement of viscoelasticity of anisotropic viscoelastic phantom by dual ultrasound excitation

An estimation of anisotropic viscoelasticity is important for evaluating muscle lesions. In the previous study, we proposed a method for estimating viscoelasticity in a local region by exciting a phantom specimen from both directions. In the present study, we observed the acoustic field having the locality and directivity generated by dual ultrasound excitation. In addition, the displacement distributions for the isotropic and anisotropic viscoelastic phantoms were measured, and the local generation of large displacement and its directionality was confirmed around the excitation focal point. Furthermore, we applied our viscoelasticity estimation method to the anisotropic viscoelastic phantom. The estimated shear modulus differed depending on the angle between the opposite direction of the ultrasound transducer projected on the phantom surface and longitudinal direction of the cylindrical urethane rubber bundle in the anisotropic viscoelastic phantom. Therefore, the viscoelasticity estimation method in the present study could estimate anisotropic viscoelasticity locally.