This paper presents the three dimensional kinematic modeling of a novel steerable robotic ablation catheter system. The catheter, embedded with a set of current-carrying micro-coils, is actuated by the magnetic forces generated by the magnetic field of the MRI scanner. This paper develops a 3D model of the MRI actuated steerable catheter system by using finite differences approach. For each finite segment, a quasi-static torque-deflection equilibrium equation is calculated using beam theory. By using the deflection displacements and torsion angles, the kinematic modeling of the catheter system is derived. The proposed models are evaluated by comparing the simulation results of the proposed model with the experimental results of a proof-of-concept prototype.
This paper presents an iterative Jacobian-based inverse kinematics method for an MRI-guided magnetically-actuated steerable intravascular catheter system. The catheter is directly actuated by magnetic torques generated on a set of current-carrying micro-coils embedded on the catheter tip, by the magnetic field of the magnetic resonance imaging (MRI) scanner. The Jacobian matrix relating changes of the currents through the coils to changes of the tip position is derived using a three dimensional kinematic model of the catheter deflection. The inverse kinematics is numerically computed by iteratively applying the inverse of the Jacobian matrix. The damped least square method is implemented to avoid numerical instability issues that exist during the computation of the inverse of the Jacobian matrix. The performance of the proposed inverse kinematics approach is validated using a prototype of the robotic catheter by comparing the actual trajectories of the catheter tip obtained via open-loop control with the desired trajectories. The results of reproducibility and accuracy evaluations demonstrate that the proposed Jacobian-based inverse kinematics method can be used to actuate the catheter in open-loop to successfully perform complex ablation trajectories required in atrial fibrillation ablation procedures. This study paves the way for effective and accurate closed-loop control of the robotic catheter with real-time feedback from MRI guidance in subsequent research.
This paper presents design optimization of a magnetic resonance imaging (MRI) actuated steerable catheter for atrial fibrillation ablation in the left atrium. The catheter prototype, built over polymer tubing, is embedded with current-carrying electromagnetic coils. The prototype can be deflected to a desired location by controlling the currents passing through the coils. The design objective is to develop a prototype that can successfully accomplish the ablation task. To complete the tasks, the catheter needs to be capable of reaching a set of desired targets selected by a physician on the chamber and keeping a stable contact with the chamber surface. The design process is based on the maximization of the steering performance of the catheter by evaluating its workspace in free space. The selected design is validated by performing a simulation of an ablation intervention on a virtual model of the left atrium with a real atrium geometry. This validation shows that the prototype can reach every target required by the ablation intervention and provide an appropriate contact force against the chamber.
This paper presents algorithms for selection of needle grasp and for selection of entry ports of robotic instruments, for autonomous robotic execution of the minimally invasive surgical suturing task. A critical issue for automatic execution of surgical tasks, such as suturing, is the choice of needle grasp for the robotic system. Inappropriate needle grasp increases operating time requiring multiple regrasps to complete the desired task. In robotic minimally invasive surgery, the entry port that the surgical robot goes through into the patient’s body has a significant role on the performance of the robot. Improper entry port affects the robot’s dexterity, manipulability and reachability. The proposed methods use manipulability, dexterity and torque metrics for needle grasp selection, and employ needle grasp robustness and target location robustness metrics for port selection. The results of a case study simulation in thoracoscopic surgery is also presented to demonstrate the proposed methods. Note to Practitioners—This paper is motivated by the problem of automating low-level surgical tasks in robotic surgery, such as, suturing, retraction, dissection, and providing exposure. Specifically, this paper focuses on needle grasp and entry port selection for automating robotic surgical suturing. Selection of an appropriate way of grasping a needle is critical for successfully and robustly completing autonomous suturing. To the best authors’ knowledge, there are no earlier studies in the literature which focus on the needle grasp selection problem. The proposed approach determines how to grasp the needle by optimizing the surgical system’s manipulation performance. The existing approaches in the literature for selecting entry ports for the robotic surgical tools only consider the teleoperated robotic minimally invasive surgery, in which the surgeons directly control the robotic instruments. However, automated performance of suturing introduces additional challenges due to uncertainties in needle localization and grasping. This paper proposes two new performance metrics on selecting port locations from the perspective of autonomously performing surgical suturing, without direct involvement of the human user. The paper also presents preliminary experiments which demonstrate the effectiveness of the proposed methods.
An MRI-actuated catheter is a novel robotic catheter system that utilizes the MRI for both remote steering and visualization for catheter ablation of atrial fibrillation. Planning and control of the catheter requires a sufficiently fast yet accurate model of the catheter. The pseudo-rigid-body (PRB) model offers a reasonable trade-off between speed and accuracy by approximating the continuum catheter as rigid links connected by flexible joints, thus reducing the infinite degrees of freedom of the continuum mechanism to a finite one. In this paper, a PRB model of the MRI-actuated catheter is validated experimentally by comparing the deflections of the PRB model with the deflections of the catheter prototype.
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