Effects of Driver Placement and Phase on Multi-actuator Magnetic Resonance Elastography via Finite Element Analysis

Multi-actuator magnetic resonance elastography (MRE) has previously been studied for overcoming wave attenuation and generating uniform displacements throughout a targeted imaging region. While the actuators’ locations, relative phase offsets, and angles are known to influence the generated displacements, their effects are dependent on the geometry and properties of the specific target. Experimental optimization of these MRE parameters can be performed but is time-consuming. Alternatively, finite element analysis (FEA) is used for three-dimensional model-specific characterization of displacement fields induced by MRE mechanical excitation loads across varying actuator locations. Cubic, tissue-like homogeneous and heterogeneous models were created and loads were applied to simulate single actuator and multi-actuator cases. Multi-actuator cases were phase-matched to promote constructive interference of the induced waves. An additional investigation was performed by repeating a single multi-actuator configuration with various loading angles in the heterogeneous model. The mean displacement amplitudes and the corresponding standard deviations throughout the imaging target volumes are compared across the multiple configurations. Wave images of selected configurations are presented for comparison. Multi-actuator configurations induced the greatest mean z displacement amplitudes within the imaging target of both models. To further increase the z displacement, the excitation loads can be angled towards the imaging target. The differences in simulated displacement fields demonstrate the potential for future automated parameter optimization for closed-loop MRE driver positioning using more complex FEA models.