LONGITUDINAL DRIVER BASED MAGNETIC RESONANCE ELASTOGRAPHY

Abstract

Magnetic Resonance Elastography (MRE) is a non-invasive imaging technique used to determine the elastic properties of biological tissues. It can be used to aid the diagnosis of pathologies (such as tumors and fibrosis) which result in the variation of tissue stiffness. In this thesis, a MR elastography system was developed for use in a clinical setting. A pressure-based longitudinal driver was built to generate the shear waves. An elastography pulse sequence with motion encoding gradients was designed based on the gradient-echo and the spin-echo sequences. The pulse sequence included the ability to switch the motion encoding along any of the three coordinate axes depending on the direction of motion to be measured. Wave images were obtained by acquiring phase data for different time offsets in the motion cycle. An elastogram was computed from the phase data using the Local Frequency Estimation (LFE) algorithm. The validity of the method was experimentally verified using silicone and agar gel phantoms of varying stiffnesses. The performance of the gradient-echo and spin-echo sequences were investigated for different motion encoding gradient parameters.