Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Biomedical Engineering

Supervisor

Maria Drangova

Abstract

Many vascular and cardiac diseases are diagnosed and treated using a medical technique known as percutaneous transluminal catheter intervention (PTC). In PTC, the interventionalist inserts a catheter into the vasculature, and using the vessel as the guiding passageway, the catheter is navigated to desired anatomical targets where it would be used for various purposes such as catheter ablation for the treatment/management of cardiac arrhythmias. The catheterization procedure is conventionally guided with x-ray fluoroscopic imaging and more recently, but rarely, with Magnetic Resonance Imaging (MRI). X-ray imaging irradiates the patient directly during the procedure, and the staff and interventionalists indirectly through scattered radiation at lower dose levels, but on a daily basis. Furthermore, fluoroscopic x-ray imaging only provides 2 dimensional projection images with low anatomical soft tissue contrast. Contrary to fluoroscopy, MRI is not a source of ionizing radiation, allows 3 dimensional visualization and localization, and provides very high soft tissue contrast. However, the closed bore of conventional MRI scanners limits patient access and hinders catheter manipulation by the interventionalist.

This thesis presents the design, development and validation of an MRI-compatible master-slave catheter navigation system that allows the interventionalist to perform the catheterization procedure remotely using the guidance of MRI or x-ray fluoroscopic imaging. For MRI compatibility the robot was actuated with non-magnetic Ultrasonic motors. To permit dynamic control of the robot, a robust control servomechanism was designed and developed to allow for robust motion control of ultrasonic motors for prolonged periods. A non-magnetic sterilizable robot was designed and developed that allowed for manipulation of conventional steerable catheters, of various gauges, with 3 degrees of freedom. The interventionalist interacts with the remote catheter navigation system (RCNS) using a user-friendly master unit. The motions imparted by the user on the master are measured by the control servomechanism and used to control the robot such that the catheter follows the user’s intended motion.

Evaluation of the system, ex vivo, under real-time MRI guidance showed that the system is fully MRI-compatible and allows accurate remote motion control of the catheter tip without degrading the MR image quality. In vivo experiments in porcine models showed that the proposed RCNS is safe and allows remote navigation under fluoroscopic imaging, with high accuracy, and without significantly affecting the navigation time or fluoroscopy time. The system was successfully used to remotely deliver effective ablation lesions to desired anatomical targets within the subject’s heart. The presented RCNS takes advantage of the interventionalist’s existing dexterous skills, and does not require any prior training. This system alleviates the work hazards of fluoroscopically guided catheterization, and facilitates MRI-guided catheterization in conventional closed bore scanners.

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