DEVELOPMENT OF A KINETIC MODEL FOR STEERABLE CATHETERS FOR MINIMALLY INVASIVE SURGERY

The steerable catheters have demonstrated many advantages to overcome the limitations of the conventional catheters in the minimally invasive surgery. The motion and force transmission from the proximal end to distal tip of the catheter have significant effects to the efficiency and safety of surgery. While the force information between the catheter and the body (e.g., vessel) can be obtained by mounting sensors on the distal tip of the catheter, this would be more intrusive and less reliable than the one without the sensors, which is described in this disseration. In addition, the small diameters of the catheters may also restrict the idea of mounting sensors on the distal tip. The other approach to obtain the force information is to infer it from the information outside the body. This will demand an accurate mathematical model that describes the force and motion relation called kinetic model, and unfortunately, such a kinetic model is not available in the literature. In this dissertation, a kinetic model for steerable catheters is presented wich captures the following characteristics of the steerable catheter, namely (1) the geometrical non-linear behavior of the catheter in motion, (2) the deformable pathway, (3) the friction between the catheter and the pathyway, and (4) the contact between the catheter and pathway. A non-linear finite element system (SPACAR) was employed to capture these characteristics. A test-bed was built and an experiment was carried out to verify the developed kinetic model. The following conclusions can be drawn from this dissertation: (1) the developed kinetic model is accurte in comparison with those in literature; (2) the Dahl friction model, the LuGre friction model and the simplified LuGre friction model are able to capture the friction behavior between the catheter and the pathway but the Coulomb friction model fails (as it cannot capture the hysteresis property which has a significant influence on the behavior of the catheter); (3) the developed kinetic model has the potential of being used to optimize the design and operation of steerable catheters with several salient findings that (3a) the maximal contact force between the catheter and the pathway occurs on the tip of the distal part or the connecting part between the distal part and catheter body of the catheter and (3b) the rigidity and length of the distal part are crucial structural parameters that affect the motion and force transmission significantly. There are several contributions made by this dissertation. In the field of the steerable catheter, biomechanics and bio-instrumentation, the contributions are summarized in the following: (1) the approach to develop the kinetic model of the steerable catheter in a complex work environment is useful to model other similar compliant medical devices, such as endoscope; (2) the kinetic model of the steerable catheter can provide the force information to improve the efficiency and safety of MIS (minimally invastive surgery) and to realize the “doctor-assisted” catheter-based MIS procedure; (3) the kinetic model can provide accurate data for developing other simplified models for the steerable catheters in their corresponding work environments for realizing the robotic-based fully automated MIS procedure. (4) The kinetic model of the steerable catheter and the test-bed with the corresponding instruments and methods for the kinetic and kinematic measurements are a useful design validation in the steerable catheter technology as well as for the training of physicians to perform the catheter-based interventional procedure by adding more complex anatomic phantoms. In the field of continuum manipulator and continuum robots, the approach to develop the kinetic model is useful to model other manipulators and robots, such as snake-like robots

MR Safe Robotic Manipulator for MRI-Guided Intracardiac Catheterization

This paper introduces a robotic manipulator to realize robot-assisted intracardiac catheterization in magnetic resonance imaging (MRI) environment. MRI can offer high-resolution images to visualize soft tissue features such as scars or edema. We hypothesize that robotic catheterization, combined with the enhanced monitoring of lesions creation using MRI intraoperatively, will significantly improve the procedural safety, accuracy, and effectiveness. This is designed particularly for cardiac electrophysiological (EP) intervention, which is an effective treatment of arrhythmia. We present the first MR Safe robot for intracardiac EP intervention. The robot actuation features small hysteresis, effective force transmission, and quick response, which has been experimentally verified for its capability to precisely telemanipulate a standard clinically used EP catheter. We also present timely techniques for real-time positional tracking in MRI and intraoperative image registration, which can be integrated with the presented manipulator to im prove the performance of teleoperated robotic catheterization

Design and Modeling of Multi-Arm Continuum Robots

Continuum robots are snake-like systems able to deliver optimal therapies to pathologies deep inside the human cavity by following 3D complex paths. They show promise when anatomical pathways need to be traversed thanks to their enhanced flexibility and dexterity and show advantages when deployed in the field of single-port surgery. This PhD thesis concerns the development and modelling of multi-arm and hybrid continuum robots for medical interventions. The flexibility and steerability of the robot’s end-effector are achieved through concentric tube technology and push/pull technology. Medical robotic prototypes have been designed as proof of concepts and testbeds of the proposed theoretical works.System design considers the limitations and constraints that occur in the surgical procedures for which the systems were proposed for. Specifically, two surgical applications are considered. Our first prototype was designed to deliver multiple tools to the eye cavity for deep orbital interventions focusing on a currently invasive intervention named Optic Nerve Sheath Fenestration (ONSF). This thesis presents the end-to-end design, engineering and modelling of the prototype. The developed prototype is the first suggested system to tackle the challenges (limited workspace, need for enhanced flexibility and dexterity, danger for harming tissue with rigid instruments, extensive manipulation of the eye) arising in ONSF. It was designed taking into account the clinical requirements and constraints while theoretical works employing the Cosserat rod theory predict the shape of the continuum end-effector. Experimental runs including ex vivo experimental evaluations, mock-up surgical scenarios and tests with and without loading conditions prove the concept of accessing the eye cavity. Moreover, a continuum robot for thoracic interventions employing push/pull technology was designed and manufactured. The developed system can reach deep seated pathologies in the lungs and access regions in the bronchial tree that are inaccessible with rigid and straight instruments either robotically or manually actuated. A geometrically exact model of the robot that considers both the geometry of the robot and mechanical properties of the backbones is presented. It can predict the shape of the bronchoscope without the constant curvature assumption. The proposed model can also predict the robot shape and micro-scale movements accurately in contrast to the classic geometric model which provides an accurate description of the robot’s differential kinematics for large scale movements

Deep Reinforcement Learning in Surgical Robotics: Enhancing the Automation Level

Surgical robotics is a rapidly evolving field that is transforming the landscape of surgeries. Surgical robots have been shown to enhance precision, minimize invasiveness, and alleviate surgeon fatigue. One promising area of research in surgical robotics is the use of reinforcement learning to enhance the automation level. Reinforcement learning is a type of machine learning that involves training an agent to make decisions based on rewards and punishments. This literature review aims to comprehensively analyze existing research on reinforcement learning in surgical robotics. The review identified various applications of reinforcement learning in surgical robotics, including pre-operative, intra-body, and percutaneous procedures, listed the typical studies, and compared their methodologies and results. The findings show that reinforcement learning has great potential to improve the autonomy of surgical robots. Reinforcement learning can teach robots to perform complex surgical tasks, such as suturing and tissue manipulation. It can also improve the accuracy and precision of surgical robots, making them more effective at performing surgeries

A Method of Decreasing Time Delay for A Tele-surgery System

Abstract -The haptics-based master-slave system for Minimally Invasive Surgery is a promising way to protect surgeons from long time radiation and to train novice doctors to learn basic wire or catheter handling skills. However, the time delay of transmission of visual video and the time difference between image information and force signals restrict the application of this technology in some extent. In this paper, we proposed a new method to reduce time delay effectively. At the slave side, the tip of the active catheter is tracked in real time to provide information on the location of the catheter in the blood vessel model. And then transmitted the coordinate values to the master site. At the master site, the location of the catheter was reappeared in the navigation chart which is the same structure with the blood vessels at master side according to the coordinate values received from the slave side. Therefore the transmission time of image information is decreased. Experimental results are given to illustrate the accuracy of our method

A Platform for Robot-Assisted Intracardiac Catheter Navigation

Steerable catheters are routinely deployed in the treatment of cardiac arrhythmias. During invasive electrophysiology studies, the catheter handle is manipulated by an interventionalist to guide the catheter's distal section toward endocardium for pacing and ablation. Catheter manipulation requires dexterity and experience, and exposes the interventionalist to ionizing radiation. Through the course of this research, a platform was developed to assist and enhance the navigation of the catheter inside the cardiac chambers. This robotic platform replaces the interventionalist's hand in catheter manipulation and provides the option to force the catheter tip in arbitrary directions using a 3D input device or to automatically navigate the catheter to desired positions within a cardiac chamber by commanding the software to do so. To accomplish catheter navigation, the catheter was modeled as a continuum manipulator, and utilizing robot kinematics, catheter tip position control was designed and implemented. An electromagnetic tracking system was utilized to measure the position and orientation of two key points in catheter model, for position feedback to the control system. A software platform was developed to implement the navigation and control strategies and to interface with the robot, the 3D input device and the tracking system. The catheter modeling was validated through in-vitro experiments with a static phantom, and in-vivo experiments on three live swines. The feasibility of automatic navigation was also veri ed by navigating to three landmarks in the beating heart of swine subjects, and comparing their performance with that of an experienced interventionalist using quasi biplane fluoroscopy. The platform realizes automatic, assisted, and motorized navigation under the interventionalist's control, thus reducing the dependence of successful navigation on the dexterity and manipulation skills of the interventionalist, and providing a means to reduce the exposure to X-ray radiation. Upon further development, the platform could be adopted for human deployment

Towards Closed-loop, Robot Assisted Percutaneous Interventions under MRI Guidance

Image guided therapy procedures under MRI guidance has been a focused research area over past decade. Also, over the last decade, various MRI guided robotic devices have been developed and used clinically for percutaneous interventions, such as prostate biopsy, brachytherapy, and tissue ablation. Though MRI provides better soft tissue contrast compared to Computed Tomography and Ultrasound, it poses various challenges like constrained space, less ergonomic patient access and limited material choices due to its high magnetic field. Even after, advancements in MRI compatible actuation methods and robotic devices using them, most MRI guided interventions are still open-loop in nature and relies on preoperative or intraoperative images. In this thesis, an intraoperative MRI guided robotic system for prostate biopsy comprising of an MRI compatible 4-DOF robotic manipulator, robot controller and control application with Clinical User Interface (CUI) and surgical planning applications (3DSlicer and RadVision) is presented. This system utilizes intraoperative images acquired after each full or partial needle insertion for needle tip localization. Presented system was approved by Institutional Review Board at Brigham and Women\u27s Hospital(BWH) and has been used in 30 patient trials. Successful translation of such a system utilizing intraoperative MR images motivated towards the development of a system architecture for close-loop, real-time MRI guided percutaneous interventions. Robot assisted, close-loop intervention could help in accurate positioning and localization of the therapy delivery instrument, improve physician and patient comfort and allow real-time therapy monitoring. Also, utilizing real-time MR images could allow correction of surgical instrument trajectory and controlled therapy delivery. Two of the applications validating the presented architecture; closed-loop needle steering and MRI guided brain tumor ablation are demonstrated under real-time MRI guidance