Estudo paramétrico das propriedades mecânicas de lentes acústicas do tipo core-shell para geração de feixes superfocalizados

Abstract

Ultrasound is a safe, non-invasive, and cost-effective clinical imaging modality widely used in medical diagnostics and non-destructive testing. However, despite all current advances, due to its classical nature, the lateral resolution of ultrasound imaging systems is limited to one wavelength of the incident beam. This limitation is known as the diffraction limit. Superfocused beams generated by sphere-shaped lenses have attracted attention due to their simplicity and effectiveness in producing high resolution images and in the task of overcoming the diffraction limit. These beams are generated on the shadow side of the lens after scattering an incidente ultrasound field. Due to the dependence of these beams on the mechanical parameters of the lens, a detailed study of the lens properties is necessary to optimize high resolution imaging systems and applications. Thus, the present dissertation aims at the parametric study of the mechanical properties of core-shell acoustic lenses through numerical simulations. To carry out this study, we used the Finite Element Method (FEM) through the commercial software COMSOL Multiphysics. All simulations were performed with the lens submerged in an ideal fluid and irradiated by a plane wave with a frequency of 1MHz and wavelength λ = 1.49 mm, where we varied the mechanical properties and dimensions of the lens core-shell. Our simulations used the modules Pressure Acoustics, Frequency Domain and Solid Mechanics, where the characteristic parameters of the generated superfocused beams were then calculated. Our results showed that the parameters of beams generated with a Rexolite shell and fluid cores are more sensitive compared to metallic cores, so that the former have greater versatility in terms of applications in high resolution systems. By varying the core radius and the shell thickness, we obtained expressive variations in the parameters of the beams. This study can be a useful tool for designing new single-element transducers for applications in high-resolution imaging systems.