Design and Control of Magnetic Resonance-Compatible, Pneumatic Actuators and Robotic Platforms for Steerable Needle Interventions
Comber, David Benjamin
This dissertation presents the design and validation of a robotic platform to control steerable needles under magnetic resonance imaging (MRI) guidance. The use of MRI to guide needle-based interventions provides clinicians with informative data, including excellent visualization of soft tissue, needle placement confirmation, and thermal dose monitoring. Additionally, the patient stands to benefit from the minimally-invasive and radiation-free nature of MRI-guided interventions. However, because the closed, narrow bore of high-field MRI scanners substantially limits clinician access to the patient during imaging, many interventions require the use of a compact robot to help deliver the needle to the target under MRI guidance. Such a robot must satisfy the challenging requirements of safety, precision, compactness, and magnetic resonance (MR)-compatibility. Numerous potential interventions have yet to be realized because the majority of MR-compatible robots reported to date were designed in an anatomy-specific way and are thus difficult to apply to other anatomical targets. Therefore, the goal of the work described herein is to develop a modular robotic platform to actuate concentric tube steerable needles, a class of continuum robot applicable to treatment of a broad range of anatomical structures. The design, fabrication, and control of two, multiple degree-of-freedom prototypes are described. To the author’s knowledge, the first prototype is the first fully-pneumatic MR-compatible robot to be reported for neurosurgical applications. The main contributions of the second prototype are hybrid pneumatic control for precise and intrinsically-safe operation, and novel designs of bellows actuators additively manufactured for compactness and hermetic sealing. To enable a novel, foramen ovale approach to epilepsy treatment using the modular MR-compatible robot, prototypes of a non-invasive head holder, a helical needle, and a radiofrequency ablation electrode are presented. Finally, the potential applicability of this non-invasive approach to a wide range of patients is explored. Designed using nonlinear optimization, curvilinear concentric tube needle trajectories are shown to accurately traverse the medial axis of the hippocampus for twenty different cases. The results herein collectively contribute robotic hardware and controls to help transform deep brain therapy from open surgery to a minimally-invasive procedure.