A Novel FEM-Based Numerical Solver for Interactive Catheter Simulation in Virtual Catheterization

Virtual reality-based simulators are very helpful for trainees to acquire the skills of manipulating catheters and guidewires during the vascular interventional surgeries. In the development of such a simulator, however, it is a great challenge to realistically model and simulate deformable catheters and guidewires in an interactive manner. We propose a novel method to simulate the motion of catheters or guidewires and their interactions with patients' vascular system. Our method is based on the principle of minimal total potential energy. We formulate the total potential energy in the vascular interventional circumstance by summing up the elastic energy deriving from the bending of the catheters or guidewires, the potential energy due to the deformation of vessel walls, and the work by the external forces. We propose a novel FEM-based approach to simulate the deformation of catheters and guidewires. The motion of catheters or the guidewires and their responses to every input from the interventionalist can be calculated globally. Experiments have been conducted to validate the feasibility of the proposed method, and the results demonstrate that our method can realistically simulate the complex behaviors of catheters and guidewires in an interactive manner

Automated planning for robotic guidewire navigation in the coronary arteries

International audienceSoft continuum robots, and comparable instruments allow to perform some surgical procedures noninvasively. While safer, less morbid and more cost-effective, these medical interventions increase the complexity for the practitioners: the manipulation of anatomical structures is indirect through telescopic and flexible devices and the visual feedback is indirect through monitors. Interventional cardiology is an example of complex procedures where catheters and guidewires are manipulated to reach and treat remote areas of the vascular network. Such interventions may be assisted with a robot that will operate the tools but the planning (choice of tools and trajectories) remains a complex task. In this paper we use a simulation framework for flexible devices inside the vasculature and we propose a method to automatically control these devices to reach specific locations. Experiments performed on 15 patient geometries exhibit good performance. Automatic manipulation reaches the goal in more than 90% of the cases

Design, Development and Force Control of a Tendon-driven Steerable Catheter with a Learning-based Approach

In this research, a learning-based force control schema for tendon-driven steerable catheters with the application in robot-assisted tissue ablation procedures was proposed and validated. To this end, initially a displacement-based model for estimating the contact force between the catheter and tissue was developed. Afterward, a tendon-driven catheter was designed and developed. Next, a software-hardware-integrated robotic system for controlling and monitoring the pose of the catheter was designed and developed. Also, a force control schema was developed based on the developed contact force model as a priori knowledge. Furthermore, the position control of the tip of the catheter was performed using a learning-based inverse kinematic approach. By combining the position control and the contact model, the force control schema was developed and validated. Validation studies were performed on phantom tissue as well as excised porcine tissue. Results of the validation studies showed that the proposed displacement-based model was 91.5% accurate in contact force prediction. Also, the system was capable of following a set of desired trajectories with an average root-mean-square error of less than 5%. Further validation studies revealed that the system could fairly generate desired static and dynamic force profiles on the phantom tissue. In summary, the proposed force control system did not necessitate the utilization of force sensors and could fairly contribute in automatizing the ablation task for robotic tissue ablation procedures

Development of A Kinetic Model For Loop-Free Colonoscopy Technology

The colonoscope is an important tool in diagnosis and management of diseases of the colon. One of the ongoing challenges with this device is that the colonoscope may form a loop together with the colon during the procedure. The result of the loop is that further insertion of the scope in the colon may not be possible. The loop may also cause risks of perforation of the colon and pain in the patient. There are currently several existing devices to overcome loop formation in colonoscopy, some of which have been introduced in clinical work. However, empirical assessment shows that these devices do not work very well. This is the motivation for the research presented in this thesis. In this thesis, a new paradigm of thinking, “doctor-assisted colonoscopy,” is proposed to overcome loop formation. In this new approach, the physician’s role is enhanced with new information that is acquired by sensors outside the human body and inferred from the mathematical model. It is referred to as a kinetic model due to the fact that this model describes the kinetic behaviour of the scope. This thesis is devoted to development of this kinetic model. In this study, the model of the colonoscope and the model of the colon are developed based on the Timoshenko beam theory, and parameters in both models are determined by the experiments. The following conclusions then are made: (1) self-locking of the colonoscope is the most basic cause for a loop to occur, while structural instability of the colonsocope is dependent on the self-locking; (2) both the scope and the colon can be well represented with the Timoshenko beam elements and the Linear Complementary Problem (LCP) formulation derived from Signorini’s law, and Coulom’s law for representation of interactions between the colon and scope is adequate; (3) there are effects from the location, looping, and tip deflection of the scope on flexural rigidity of the scope. Approximately, the flexural rigidity of the CF-Q160L colonoscope ranges from 300 to 650 N•cm2, and its accuracy is proven by a good agreement between the model predicted result and experimental result; (4) Rayleigh damping for the CF-Q160L colonoscope depends more on the mass matrix [M] of the colonoscope than the stiffness matrix [K], which is evident by the large coefficient value of “alpha” (0.3864) and the small coefficient value of “beta” (0.0164). The contributions of this thesis are: (1) the finding that the main cause of the loop is not structural instability of the colonoscope but rather self-locking of the colonoscope, which could lead to design of a “new-generation” colonoscope to avoid the loop; (2) a systematic evaluation of the existing colonoscopy technologies based on the well-proven Axiomatic Design Theory (ADT), which will serve as a guideline for the development of future new colonoscopes in future; (3) an approach to developing a kinetic model of the colonoscope useful to modeling similar objects such as a catheter guide-wire; (4) a novel ex-vivo colonoscopy test-bed with the kinetic and kinematic measurements useful for validation of new designs in colonoscopy technology and also useful for training physicians who perform the colonoscopy procedure; and (5) a new paradigm of thinking for colonoscopy called “doctor-assisted colonoscopy,” which has potential applications to other medical procedures such as catheter-based procedures

Predictive surgical simulation for preoperative planning of complex cardioviscular surgeries

Ph.DDOCTOR OF PHILOSOPH

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

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

Angiovision - Pose d'endoprothèse aortique par angionavigation augmentée

Nous avons développé un modèle numérique du traitement des anévrismes de l'aorte abdominale (AAA) en utilisant l'analyse par éléments finis (FEA). L'objectif est de simuler les différentes étapes de la procédure endovasculaire dans la phase préopératoire. Pour cela, dans un premier temps, on a fait des études expérimentales Macro et Nano de rupture, indentation, traction, frottement des outils métalliques et des biomatériaux. Ensuite, on a développé une nouvelle approche de la conception des structures anatomiques très angulées et hétérogènes, et enfin, on a crée une maquette numérique de l interaction outils métalliques et biomatériaux. Dans ce modèle, nous avons pris en compte la géométrie réelle reconstituée à partir des scans, une caractérisation locale des propriétés mécaniques guide / cathéter, une cartographie des propriétés des matériaux composites en fonction de la qualité pariétale, et une projection de l'environnement de l artère dans l outil de simulation. Nos résultats ont été validés grâce à un recalage entre les données cliniques et notre simulation pour un groupe donné de patients, dont les artères sont très tortueuses et calcifiées. Cet outil d aide à l acte chirurgical permet de contrôler avec précision la navigation endovasculaire en péropératoire, prédire la faisabilité de la chirurgie avec une fiabilité ainsi que d optimiser le nombre d outils métalliques pour chaque patient, en tenant compte du risque de rupture des zones avec fortes tortuosités et hétérogénéités.We have developed a numerical model of the treatment of abdominal aortic aneurysms (AAA) using finite element analysis (FEA) to simulate the endovascular procedure in the preoperative phase. The goal is to simulate different stages of the endovascular procedure. In the model, we took into account the geometry of the biological region reconstructed from scans, a local characterization of the guidewire/catheter mechanical properties, a mapping of material properties depending on the degree of calcification, and a projection of the aorta environment . Our results were validated based on a tuning between clinical data and our simulation for a given group of patients with very tortuous and calcified arteries. It allows to control with accuracy the delivery system rise during surgery, predict the feasibility of the surgery with reliability as well as choose the best guide for each patient, taking into account the risk of rupture of calcified areas in the case of high angulations.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF

Development of Techniques for Modeling the Static Buckling of Euler Beam and Dynamic Response of Kirchhoff Rods: Application to Surgical Simulation and Training

In this dissertation, we present novel schemes for a static simulation of a buckled Euler beam with curve channel constraints in two dimensional space and simulation of the dynamic response of a soft Kirchhoff rod in three dimension space at real time rate. The aim of this model is to provide a robust and fast means for simulating endoscopes and surgical threads for training and surgical simulation purposes. Finding a static configuration of a buckled cantilever elastic beam constrained in a curved solid channel subject to end forces is a simple model of endoscopy and it is posed as the minimization of an energy functional. We solve it by a novel technique, a variant of a dynamic programming approach called the Viterbi algorithm. The core idea of this approach is to discretize the variables describing the potential energy and to construct a set of admissible configurations of the beam. The Viterbi algorithm is then employed to search through the set of possible beam configurations and locate the one with the minimum potential energy in a very computationally efficient way. The new approach does not require any gradient computations and could be considered as a direct search method, and thus can be guaranteed to find the global minimum potential energy. Also the constraints can be automatically satisfied by constructing the proper set of all the possible configurations. The approach can also be used to find feasible starting configurations associated with conventional minimizing algorithms. We also discuss a novel scheme based on discrete variational integrators to study the dynamics of an inextensible thin Kirchhoff rod which is a model for a surgical thread. The benefits of such approach are that it is a very efficient scheme that guarantees conservation of momentum and energy over very long times so that a real time simulator can be operated over long periods of time. In addition, we report on an innovative technique to capture the inextensibility as well as the internal dissipation of the rod efficiently. Finally, a new collision avoidance scheme based on a continuous penalty force is employed to simulate the interaction of the rod with the surrounding medium. The simulations performed capture the formation of plectoneme, i.e. a loop of helices twisted together. Lastly, the scheme is employed to simulate the tying of a square knot. This model can be used to simulate surgical threads at real time rate