Robots and Fibres for MR-Guided Endovascular Interventions
Creators: name: Abdelaziz, Mohamed
Publisher: name: Imperial College London
Year: 2021

description: Interventional radiology and cardiology are rapidly growing areas of minimally invasive surgery, covering multiple diagnostic and interventional procedures. Treatment via endovascular techniques has become the go-to approach, thanks to its minimally invasive nature and its effectiveness in reducing hospitalisation and total time to recovery when compared to open surgery. Although X-ray fluoroscopy is currently the gold standard imaging technique for endovascular interventions, it presents occupational safety hazards to medical personnel and potential risks to patients, especially paediatric patients, because of its inherent ionising radiation. Magnetic resonance imaging (MRI), with its unique ability to provide radiation free imaging, and acquiring morphologic and functional information, holds great promise in the advancement of image-guided navigation through the vasculature. Moreover, MRI has the potential to combine diagnosis, therapy and early evaluation of therapy in the same intervention. However, MR-guided interventions face major challenges due to the limited accessibility to patients (especially paediatric patients), excessive noise levels within the room which impede the communication between the medical personnel, and most prominently, the lack of MR safe and compatible instruments. This thesis addresses these challenges in two main stages. The first centres on the development of a robotic platform that aims to improve the precision, safety, access, comfort and to minimise and possibly eliminate radiation exposure for the patient and medical personnel. The master-slave system allows clinicians to remotely manipulate commercially available instrumentation and in-house fabricated steerable catheters. The platform comprises a master manipulator that emulates conventional manipulation of instruments and offers haptic-feedback to the operator. In addition, the slave robot is pneumatically actuated using 3D printed linear and rotary stepper motors. The robotic system not only reduces the medical personnel’s exposure to ionising radiation when used under X-ray fluoroscopy guidance, but also paves the way for endovascular interventions under MR as a result of the slave robot’s polymeric nature. Assessment experiments under X-ray fluoroscopy guidance demonstrated the feasibility of the platform through clinically relevant endovascular tasks performed by clinical experts in an in-vitro phantom study. Subsequently, an animal study with an expert endovascular surgeon validated its efficacy and safety, by achieving lower occurrence and severity of injuries (as per post-mortem histopathological assessment). The second complementing stage leverages the unconventional scalable fibre drawing technique to address the gap in MR safe instrumentation. By exploiting its unique advantages, a new low-cost rapid prototyping platform for the fabrication of arbitrary cross-sections and high aspect ratio materials, is presented, which aims to accelerate technology translation in the field of minimally invasive surgery. Using this technology, a novel 7Fr MR safe and passively visible steerable catheter was developed to navigate through the anatomy under MR-guidance. Thorough bench-top mechanical characterisation of the polymer-based catheter showed comparable mechanical performance, which did not differ significantly from the commercial metal-braided selective and steerable catheters on the market today. Real-time MR image guidance of the in-house fabricated catheter was demonstrated in a vessel phantom under a clinical 3 Tesla MR scanner to evaluate the catheter’s mechanical efficacy and MR visibility. Small vascular structures, such as the renal artery, could be probed efficiently with the polymer-only based catheter. With the integrated iron markers, it was visible in its entirety, and the limited artefact size allowed for the effective visualisation of surrounding tissue. Moreover, the catheter’s steerability, visibility and safety were successfully demonstrated in a porcine model. Lastly, in an attempt to demonstrate the future potential of the work presented in this thesis, the robotic platform is extended to host the steerable catheter, paving the way for further testing under MR-guidance.