MRI Compatible Piezoelectric Actuator Development and Towards Application Based Simulation

Zhao, Zhanyue Jimmy

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MRI Compatible Piezoelectric Actuator Development and Towards Application Based Simulation

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Precise surgical procedures may benefit from intra-operative image guidance using magnetic resonance imaging (MRI). However, the MRI’s strong magnetic fields, fast switching gradients, and constrained space pose the need for specially designed MR-guided robotic systems. Piezoelectric ultrasonic motor (USM) is one type of MRI-compatible actuator that can actuate these robots with fast response times, compactness, and simple configuration. Although the piezoelectric motors are mostly made of nonferromagnetic material, the eddy currents and motor vibrations can further degrade image quality by causing image artifacts. On the therapy delivery side of MRI-compatible actuators, even though the current MRI-guided piezoelectrically actuated interstitial thermal ablation technique for tumor intervention can be assisted with numerical modeling, it is still challenging to predict transient temperature profiles and assess tissue damage upon heating with absolute accuracy. This dissertation addressed the above challenges of developing and utilizing piezoelectric actuators, with applications to robot motion and thermal therapy delivery. We developed a plastic USM with a greater degree of MRI compatibility, and a finite element modeling (FEM) simulation for rotary USM traveling wave friction-driven stator-rotor coupling system using COMSOL Multiphysics. We also developed a novel custom-made hollow cylindrical motor (HCM), and a preliminary prototype of a differential drive system aiming to achieve the insertion and rotation of biopsy needle manipulation. In addition, we developed a 2-dimensional (2D) thermal damage FEM simulation with brain tissue parameters for the precise ablation procedure, and validated with multiple in-vivo animal surgeries. This work was extended to generate a thermal ablation database to support conformal ablation in a further dynamic ablation study.

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