Magnetic Resonance Elastography: Multi-directional excitation in a Table Top MRI System and Finite Element Simulations of harmonic excitation experiments

Abstract There is a strong connection between changes in mechanical properties and injuries or diseases. In order to detect the mechanical structure of tissue, techniques like biopsy and manual palpation were developed. However, these methods have many drawbacks. Biopsy is invasive and not reliable, while manual palpation is qualitative, superficial, and dependent on the operator. To address these limitations, Elastography emerged as a non-invasive and quantitative way to assess tissue stiffness. This study aimed to explore the use of torsionally-polarized geometrically-focused waves induced by a stepper motor on a test tube, and to investigate whether wave propagation changes when a pre-stretch is applied to the phantom. To achieve this, the study designed a new arrangement where a cylindrical sample was suspended freely in the MRI, allowing for different axial tensile pre-stresses to be applied while simultaneously conducting Magnetic Resonance Elastography (MRE) studies. The measurements obtained through MRE included wave images depicting the displacement field in cross-sectional slices within an isotropic cylindrical phantom under varying pre-stresses. The experimental data was compared to computer simulations using finite element analysis (FEA). This investigation provides valuable insights into tissue mechanics, and offers a way to assess tissue anisotropy and wave propagation under different pre-stress conditions.