Computer-Assisted Electroanatomical Guidance for Cardiac Electrophysiology Procedures

Cardiac arrhythmias are serious life-threatening episodes affecting both the aging population and younger patients with pre-existing heart conditions. One of the most effective therapeutic procedures is the minimally-invasive catheter-driven endovascular electrophysiology study, whereby electrical potentials and activation patterns in the affected cardiac chambers are measured and subsequent ablation of arrhythmogenic tissue is performed. Despite emerging technologies such as electroanatomical mapping and remote intraoperative navigation systems for improved catheter manipulation and stability, successful ablation of arrhythmias is still highly-dependent on the operator’s skills and experience. This thesis proposes a framework towards standardisation in the electroanatomical mapping and ablation planning by merging knowledge transfer from previous cases and patient-specific data. In particular, contributions towards four different procedural aspects were made: optimal electroanatomical mapping, arrhythmia path computation, catheter tip stability analysis, and ablation simulation and optimisation. In order to improve the intraoperative electroanatomical map, anatomical areas of high mapping interest were proposed, as learned from previous electrophysiology studies. Subsequently, the arrhythmic wave propagation on the endocardial surface and potential ablation points were computed. The ablation planning is further enhanced, firstly by the analysis of the catheter tip stability and the probability of slippage at sparse locations on the endocardium and, secondly, by the simulation of the ablation result from the computation of convolutional matrices which model mathematically the ablation process. The methods proposed by this thesis were validated on data from patients with complex congenital heart disease, who present unusual cardiac anatomy and consequently atypical arrhythmias. The proposed methods also build a generic framework for computer guidance of electrophysiology, with results showing complementary information that can be easily integrated into the clinical workflow.Open Acces

Using the Fringe Field of MRI Scanner for the Navigation of Microguidewires in the Vascular System

Le traitement du cancer, la prévention des accidents vasculaires cérébraux et le diagnostic ou le traitement des maladies vasculaires périphériques sont tous des cas d'application d'interventions à base de cathéter par le biais d'un traitement invasif minimal. Cependant, la pratique du cathétérisme est généralement pratiquée manuellement et dépend fortement de l'expérience et des compétences de l'interventionniste. La robotisation du cathétérisme a été étudiée pour faciliter la procédure en augmentant les niveaux d’autonomie par rapport à cette pratique clinique. En ce qui concerne ce problème, un des problèmes concerne le placement super sélectif du cathéter dans les artères plus étroites nécessitant une miniaturisation de l'instrument cathéter / fil de guidage attaché. Un microguide qui fonctionne dans des vaisseaux sanguins étroits et tortueux subit différentes forces mécaniques telles que le frottement avec la paroi du vaisseau. Ces forces peuvent empêcher la progression de la pointe du fil de guidage dans les vaisseaux. Une méthode proposée consiste à appliquer une force de traction à la pointe du microguide pour diriger et insérer le dispositif tout en poussant l’instrument attaché à partir de l’autre extrémité n’est plus pratique, et à exploiter le gradient du champ de franges IRM surnommé Fringe Field Navigation (FFN ) est proposée comme solution pour assurer cet actionnement. Le concept de FFN repose sur le positionnement d'un patient sur six DOF dans le champ périphérique du scanner IRM afin de permettre un actionnement directionnel pour la navigation du fil-guide. Ce travail rend compte des développements requis pour la mise en oeuvre de la FFN et l’étude du potentiel et des possibilités qu’elle offre au cathétérisme, en veillant au renforcement de l’autonomie. La cartographie du champ de franges d'un scanner IRM 3T est effectuée et la structure du champ de franges en ce qui concerne son uniformité locale est examinée. Une méthode pour la navigation d'un fil de guidage le long d'un chemin vasculaire souhaité basée sur le positionnement robotique du patient à six DOF est développée. Des expériences de FFN guidées par rayons X in vitro et in vivo sur un modèle porcin sont effectuées pour naviguer dans un fil de guidage dans la multibifurcation et les vaisseaux étroits. Une caractéristique unique de FFN est le haut gradient du champ magnétique. Il est démontré in vitro et in vivo que cette force surmonte le problème de l'insertion d'un fil microguide dans des vaisseaux tortueux et étroits pour permettre de faire avancer le fil-guide avec une distale douce au-delà de la limite d'insertion manuelle. La robustesse de FFN contre les erreurs de positionnement du patient est étudiée en relation avec l'uniformité locale dans le champ périphérique. La force élevée du champ magnétique disponible dans le champ de franges IRM peut amener les matériaux magnétiques doux à son état de saturation. Ici, le concept d'utilisation d'un ressort est présenté comme une alternative vi déformable aux aimants permanents solides pour la pointe du fil-guide. La navigation d'un microguide avec une pointe de ressort en structure vasculaire complexe est également réalisée in vitro. L'autonomie de FFN en ce qui concerne la planification d'une procédure avec autonomie de tâche obtenue dans ce travail augmente le potentiel de FFN en automatisant certaines étapes d'une procédure. En conclusion, FFN pour naviguer dans les microguides dans la structure vasculaire complexe avec autonomie pour effectuer le positionnement du patient et contrôler l'insertion du fil de guidage - avec démonstration in vivo dans un modèle porcin - peut être considéré comme un nouvel outil robotique facilitant le cathétérisme vasculaire. tout en aidant à cibler les vaisseaux lointains dans le système vasculaire.----------ABSTRACT Treatment of cancer, prevention of stroke, and diagnosis or treatment of peripheral vascular diseases are all the cases of application of catheter-based interventions through a minimal-invasive treatment. However, performing catheterization is generally practiced manually, and it highly depends on the experience and the skills of the interventionist. Robotization of catheterization has been investigated to facilitate the procedure by increasing the levels of autonomy to this clinical practice. Regarding it, one issue is the super selective placement of the catheter in the narrower arteries that require miniaturization of the tethered catheter/guidewire instrument. A microguidewire that operates in narrow and tortuous blood vessels experiences different mechanical forces like friction with the vessel wall. These forces can prevent the advancement of the tip of the guidewire in the vessels. A proposed method is applying a pulling force at the tip of the microguidewire to steer and insert the device while pushing the tethered instrument from the other end is no longer practical, and exploiting the gradient of the MRI fringe field dubbed as Fringe Field Navigation (FFN) is proposed as a solution to provide this actuation. The concept of FFN is based on six DOF positioning of a patient in the fringe field of the MRI scanner to enable directional actuation for the navigation of the guidewire. This work reports on the required developments for implementing FFN and investigating the potential and the possibilities that FFN introduces to the catheterization, with attention to enhancing the autonomy. Mapping the fringe field of a 3T MRI scanner is performed, and the structure of the fringe field regarding its local uniformity is investigated. A method for the navigation of a guidewire along a desired vascular path based on six DOF robotic patient positioning is developed. In vitro and in vivo x-ray Guided FFN experiments on a swine model of are performed to navigate a guidewire in the multibifurcation and narrow vessels. A unique feature of FFN is the high gradient of the magnetic field. It is demonstrated in vitro and in vivo that this force overcomes the issue of insertion of a microguidewire in tortuous and narrow vessels to enable advancing the guidewire with a soft distal beyond the limit of manual insertion. Robustness of FFN against the error in the positioning of the patient is investigated in relation to the local uniformity in the fringe field. The high strength of the magnetic field available in MRI fringe field can bring soft magnetic materials to its saturation state. Here, the concept of using a spring is introduced as a deformable alternative to solid permanent magnets for the tip of the guidewire. Navigation of a microguidewire with a viii spring tip in complex vascular structure is also performed in vitro. The autonomy of FFN regarding planning a procedure with Task Autonomy achieved in this work enhances the potential of FFN by automatization of certain steps of a procedure. As a conclusion, FFN to navigate microguidewires in the complex vascular structure with autonomy in performing tasks of patient positioning and controlling the insertion of the guidewire – with in vivo demonstration in swine model – can be considered as a novel robotic tool for facilitating the vascular catheterization while helping to target remote vessels in the vascular system

InterNAV3D: A Navigation Tool for Robot-Assisted Needle-Based Intervention for the Lung

Lung cancer is one of the leading causes of cancer deaths in North America. There are recent advances in cancer treatment techniques that can treat cancerous tumors, but require a real-time imaging modality to provide intraoperative assistive feedback. Ultrasound (US) imaging is one such modality. However, while its application to the lungs has been limited because of the deterioration of US image quality (due to the presence of air in the lungs); recent work has shown that appropriate lung deflation can help to improve the quality sufficiently to enable intraoperative, US-guided robotics-assisted techniques to be used. The work described in this thesis focuses on this approach. The thesis describes a project undertaken at Canadian Surgical Technologies and Advanced Robotics (CSTAR) that utilizes the image processing techniques to further enhance US images and implements an advanced 3D virtual visualization software approach. The application considered is that for minimally invasive lung cancer treatment using procedures such as brachytherapy and microwave ablation while taking advantage of the accuracy and teleoperation capabilities of surgical robots, to gain higher dexterity and precise control over the therapy tools (needles and probes). A number of modules and widgets are developed and explained which improve the visibility of the physical features of interest in the treatment and help the clinician to have more reliable and accurate control of the treatment. Finally the developed tools are validated with extensive experimental evaluations and future developments are suggested to enhance the scope of the applications

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

Computer Vision Techniques for Transcatheter Intervention

Minimally invasive transcatheter technologies have demonstrated substantial promise for the diagnosis and treatment of cardiovascular diseases. For example, TAVI is an alternative to AVR for the treatment of severe aortic stenosis and TAFA is widely used for the treatment and cure of atrial fibrillation. In addition, catheter-based IVUS and OCT imaging of coronary arteries provides important information about the coronary lumen, wall and plaque characteristics. Qualitative and quantitative analysis of these cross-sectional image data will be beneficial for the evaluation and treatment of coronary artery diseases such as atherosclerosis. In all the phases (preoperative, intraoperative, and postoperative) during the transcatheter intervention procedure, computer vision techniques (e.g., image segmentation, motion tracking) have been largely applied in the field to accomplish tasks like annulus measurement, valve selection, catheter placement control, and vessel centerline extraction. This provides beneficial guidance for the clinicians in surgical planning, disease diagnosis, and treatment assessment. In this paper, we present a systematical review on these state-of-the-art methods.We aim to give a comprehensive overview for researchers in the area of computer vision on the subject of transcatheter intervention. Research in medical computing is multi-disciplinary due to its nature, and hence it is important to understand the application domain, clinical background, and imaging modality so that methods and quantitative measurements derived from analyzing the imaging data are appropriate and meaningful. We thus provide an overview on background information of transcatheter intervention procedures, as well as a review of the computer vision techniques and methodologies applied in this area

The Role of Visualization, Force Feedback, and Augmented Reality in Minimally Invasive Heart Valve Repair

New cardiovascular techniques have been developed to address the unique requirements of high risk, elderly, surgical patients with heart valve disease by avoiding both sternotomy and cardiopulmonary bypass. However, these technologies pose new challenges in visualization, force application, and intracardiac navigation. Force feedback and augmented reality (AR) can be applied to minimally invasive mitral valve repair and transcatheter aortic valve implantation (TAVI) techniques to potentially surmount these challenges. Our study demonstrated shorter operative times with three dimensional (3D) visualization compared to two dimensional (2D) visualization; however, both experts and novices applied significantly more force to cardiac tissue during 3D robotics-assisted mitral valve annuloplasty than during conventional open mitral valve annuloplasty. This finding suggests that 3D visualization does not fully compensate for the absence of haptic feedback in robotics-assisted cardiac surgery. Subsequently, using an innovative robotics-assisted surgical system design, we determined that direct haptic feedback may improve both expert and trainee performance using robotics-assisted techniques. We determined that during robotics-assisted mitral valve annuloplasty the use of either visual or direct force feedback resulted in a significant decrease in forces applied to cardiac tissue when compared to robotics-assisted mitral valve annuloplasty without force feedback. We presented NeoNav, an AR-enhanced echocardiograpy intracardiac guidance system for NeoChord off-pump mitral valve repair. Our study demonstrated superior tool navigation accuracy, significantly shorter navigation times, and reduced potential for injury with AR enhanced intracardiac navigation for off-pump transapical mitral valve repair with neochordae implantation. In addition, we applied the NeoNav system as a safe and inexpensive alternative imaging modality for TAVI guidance. We found that our proposed AR guidance system may achieve similar or better results than the current standard of care, contrast enhanced fluoroscopy, while eliminating the use of nephrotoxic contrast and ionizing radiation. These results suggest that the addition of both force feedback and augmented reality image guidance can improve both surgical performance and safety during minimally invasive robotics assisted and beating heart valve surgery, respectively

REAL-TIME 4D ULTRASOUND RECONSTRUCTION FOR IMAGE-GUIDED INTRACARDIAC INTERVENTIONS

Image-guided therapy addresses the lack of direct vision associated with minimally- invasive interventions performed on the beating heart, but requires effective intraoperative imaging. Gated 4D ultrasound reconstruction using a tracked 2D probe generates a time-series of 3D images representing the beating heart over the cardiac cycle. These images have a relatively high spatial resolution and wide field of view, and ultrasound is easily integrated into the intraoperative environment. This thesis presents a real-time 4D ultrasound reconstruction system incorporated within an augmented reality environment for surgical guidance, whose incremental visualization reduces common acquisition errors. The resulting 4D ultrasound datasets are intended for visualization or registration to preoperative images. A human factors experiment demonstrates the advantages of real-time ultrasound reconstruction, and accuracy assessments performed both with a dynamic phantom and intraoperatively reveal RMS localization errors of 2.5-2.7 mm, and 0.8 mm, respectively. Finally, clinical applicability is demonstrated by both porcine and patient imaging