High-performance tele-operated robot systems for intra-operative MRI-guided interventions

Abstract

Magnetic resonance imaging (MRI)-guided intervention has drawn increasing attention over the last decade. It is accredited to the capabilities in providing non-invasive and high-contrast images of soft tissues without harmful ionizing radiation, and also in monitoring the temperature change in thermal therapy procedures. These advantages prompted the adoption of MRI guidance for interventions ranging from biopsy, thermal therapy for tumor ablation, drug delivery to catheter-based procedures within cardiovascular system. However, the inherent working principle of MRI involves high-intensity magnetic and radiofrequency (RF) fields, which prevents the adoption of robotic systems containing ferromagnetic materials. Besides, precisely manipulating the instrument within the limited workspace of MRI bore remains challenging. This gives rise to the demand for precise tele-manipulation of interventional instruments under MRI guidance.

The major focus of this thesis is to develop high-performance systems regarding robotic tele-operation for intra-operative (intra-op) MRI-guided interventions. Key robotic components are investigated, including the high-fidelity magnetic resonance (MR) safe actuation, dexterous and compact robotic mechanism, and the real-time sensing and feedback control under MRI. MR safe high-performance hydraulic motors using diaphragm-sealed cylinders are proposed as the essential component for robotic actuation. The motor can provide tele-operated, dexterous control of interventional tools under MRI. The configurable motor designs are capable of generating unlimited range of continuous bidirectional rotation with high payload. With incorporation of the proposed MR safe motors, a robotic platform is developed for bilateral stereotactic neurosurgery under intra-op MRI guidance. The compact robotic structure can enable less invasive anchorage and the accommodation inside the MR imaging head coil with a limited workspace. The simplified workflow has been validated by a pre-clinical trial under MRI. Furthermore, an MR safe robotic manipulator is developed for intracardiac catheterization, with incorporation of the proposed MR safe motors to provide dexterous manipulation of the cardiac catheter. The robot can offer functional manipulation towards cardiac electrophysiology (EP) under MRI, which is the first of its kind. A shape tracking system is proposed for the standard cardiac catheter, integrating the tracking coils and a multi-core optical fiber with fiber Bragg gratings (FBGs). Both shape and positional tracking of the bendable section could be realized. To achieve accurate and effective feedback control of the cardiac catheter, a learning-based modeling method using the shape information from FBGs is proposed, which is implemented for autonomous robotic control. The overall performance of the shape tracking and controller was demonstrated by a simulated pulmonary vein isolation (PVI) task with ex-vivo tissue ablation.