Improved Image Guidance in TACE Procedures

Purpose of the work in this thesis is to improve the image guidance in TACE procedures. More specifically, we intend to develop and evaluate technology that permits dynamic roadmapping based on a 3D model of the liver vasculature

Continuous roadmapping in liver TACE procedures using 2D–3D catheter-based registration

PURPOSE: Fusion of pre/perioperative images and intra-operative images may add relevant information during image-guided procedures. In abdominal procedures, respiratory motion changes the position of organs, and thus accurate image guidance requires a continuous update of the spatial alignment of the (pre/perioperative) information with the organ position during the intervention. METHODS: In this paper, we propose a method to register in real time perioperative 3D rotational angiography images (3DRA) to intra-operative single-plane 2D fluoroscopic images for improved guidance in TACE interventions. The method uses the shape of 3D vessels extracted from the 3DRA and the 2D catheter shape extracted from fluoroscopy. First, the appropriate 3D vessel is selected from the complete vascular tree using a shape similarity metric. Subsequently, the catheter is registered to this vessel, and the 3DRA is visualized based on the registration results. The method is evaluated on simulated data and clinical data. RESULTS: The first selected vessel, ranked with the shape similarity metric, is used more than 39 % in the final registration and the second more than 21 %. The median of the closest corresponding points distance between 2D angiography vessels and projected 3D vessels is 4.7–5.4 mm when using the brute force optimizer and 5.2–6.6 mm when using the Powell optimizer. CONCLUSION: We present a catheter-based registration method to continuously fuse a 3DRA roadmap arterial tree onto 2D fluoroscopic images with an efficient shape similarity

Review of Journal of Cardiovascular Magnetic Resonance 2015

There were 116 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2015, which is a 14 % increase on the 102 articles published in 2014. The quality of the submissions continues to increase. The 2015 JCMR Impact Factor (which is published in June 2016) rose to 5.75 from 4.72 for 2014 (as published in June 2015), which is the highest impact factor ever recorded for JCMR. The 2015 impact factor means that the JCMR papers that were published in 2013 and 2014 were cited on average 5.75 times in 2015. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is <25 % and has been falling because the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality papers to JCMR for publication

Augmented Image-Guidance for Transcatheter Aortic Valve Implantation

The introduction of transcatheter aortic valve implantation (TAVI), an innovative stent-based technique for delivery of a bioprosthetic valve, has resulted in a paradigm shift in treatment options for elderly patients with aortic stenosis. While there have been major advancements in valve design and access routes, TAVI still relies largely on single-plane fluoroscopy for intraoperative navigation and guidance, which provides only gross imaging of anatomical structures. Inadequate imaging leading to suboptimal valve positioning contributes to many of the early complications experienced by TAVI patients, including valve embolism, coronary ostia obstruction, paravalvular leak, heart block, and secondary nephrotoxicity from contrast use. A potential method of providing improved image-guidance for TAVI is to combine the information derived from intra-operative fluoroscopy and TEE with pre-operative CT data. This would allow the 3D anatomy of the aortic root to be visualized along with real-time information about valve and prosthesis motion. The combined information can be visualized as a `merged\u27 image where the different imaging modalities are overlaid upon each other, or as an `augmented\u27 image, where the location of key target features identified on one image are displayed on a different imaging modality. This research develops image registration techniques to bring fluoroscopy, TEE, and CT models into a common coordinate frame with an image processing workflow that is compatible with the TAVI procedure. The techniques are designed to be fast enough to allow for real-time image fusion and visualization during the procedure, with an intra-procedural set-up requiring only a few minutes. TEE to fluoroscopy registration was achieved using a single-perspective TEE probe pose estimation technique. The alignment of CT and TEE images was achieved using custom-designed algorithms to extract aortic root contours from XPlane TEE images, and matching the shape of these contours to a CT-derived surface model. Registration accuracy was assessed on porcine and human images by identifying targets (such as guidewires or coronary ostia) on the different imaging modalities and measuring the correspondence of these targets after registration. The merged images demonstrated good visual alignment of aortic root structures, and quantitative assessment measured an accuracy of less than 1.5mm error for TEE-fluoroscopy registration and less than 6mm error for CT-TEE registration. These results suggest that the image processing techniques presented have potential for development into a clinical tool to guide TAVI. Such a tool could potentially reduce TAVI complications, reducing morbidity and mortality and allowing for a safer procedure

Optical flow-based vascular respiratory motion compensation

This paper develops a new vascular respiratory motion compensation algorithm, Motion-Related Compensation (MRC), to conduct vascular respiratory motion compensation by extrapolating the correlation between invisible vascular and visible non-vascular. Robot-assisted vascular intervention can significantly reduce the radiation exposure of surgeons. In robot-assisted image-guided intervention, blood vessels are constantly moving/deforming due to respiration, and they are invisible in the X-ray images unless contrast agents are injected. The vascular respiratory motion compensation technique predicts 2D vascular roadmaps in live X-ray images. When blood vessels are visible after contrast agents injection, vascular respiratory motion compensation is conducted based on the sparse Lucas-Kanade feature tracker. An MRC model is trained to learn the correlation between vascular and non-vascular motions. During the intervention, the invisible blood vessels are predicted with visible tissues and the trained MRC model. Moreover, a Gaussian-based outlier filter is adopted for refinement. Experiments on in-vivo data sets show that the proposed method can yield vascular respiratory motion compensation in 0.032 sec, with an average error 1.086 mm. Our real-time and accurate vascular respiratory motion compensation approach contributes to modern vascular intervention and surgical robots.Comment: This manuscript has been accepted by IEEE Robotics and Automation Letter

Exploiting Temporal Image Information in Minimally Invasive Surgery

Minimally invasive procedures rely on medical imaging instead of the surgeons direct vision. While preoperative images can be used for surgical planning and navigation, once the surgeon arrives at the target site real-time intraoperative imaging is needed. However, acquiring and interpreting these images can be challenging and much of the rich temporal information present in these images is not visible. The goal of this thesis is to improve image guidance for minimally invasive surgery in two main areas. First, by showing how high-quality ultrasound video can be obtained by integrating an ultrasound transducer directly into delivery devices for beating heart valve surgery. Secondly, by extracting hidden temporal information through video processing methods to help the surgeon localize important anatomical structures. Prototypes of delivery tools, with integrated ultrasound imaging, were developed for both transcatheter aortic valve implantation and mitral valve repair. These tools provided an on-site view that shows the tool-tissue interactions during valve repair. Additionally, augmented reality environments were used to add more anatomical context that aids in navigation and in interpreting the on-site video. Other procedures can be improved by extracting hidden temporal information from the intraoperative video. In ultrasound guided epidural injections, dural pulsation provides a cue in finding a clear trajectory to the epidural space. By processing the video using extended Kalman filtering, subtle pulsations were automatically detected and visualized in real-time. A statistical framework for analyzing periodicity was developed based on dynamic linear modelling. In addition to detecting dural pulsation in lumbar spine ultrasound, this approach was used to image tissue perfusion in natural video and generate ventilation maps from free-breathing magnetic resonance imaging. A second statistical method, based on spectral analysis of pixel intensity values, allowed blood flow to be detected directly from high-frequency B-mode ultrasound video. Finally, pulsatile cues in endoscopic video were enhanced through Eulerian video magnification to help localize critical vasculature. This approach shows particular promise in identifying the basilar artery in endoscopic third ventriculostomy and the prostatic artery in nerve-sparing prostatectomy. A real-time implementation was developed which processed full-resolution stereoscopic video on the da Vinci Surgical System

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

Towards Image-Guided Pediatric Atrial Septal Defect Repair

Congenital heart disease occurs in 107.6 out of 10,000 live births, with Atrial Septal Defects (ASD) accounting for 10\% of these conditions. Historically, ASDs were treated with open heart surgery using cardiopulmonary bypass, allowing a patch to be sewn over the defect. In 1976, King et al. demonstrated use of a transcatheter occlusion procedure, thus reducing the invasiveness of ASD repair. Localization during these catheter based procedures traditionally has relied on bi-plane fluoroscopy; more recently trans-esophageal echocardiography (TEE) and intra-cardiac echocardiography (ICE) have been used to navigate these procedures. Although there is a high success rate using the transcatheter occlusion procedure, fluoroscopy poses radiation dose risk to both patient and clinician. The impact of this dose to the patients is important as many of those undergoing this procedure are children, who have an increased risk associated with radiation exposure. Their longer life expectancy than adults provides a larger window of opportunity for expressing the damaging effects of ionizing radiation. In addition, epidemiologic studies of exposed populations have demonstrated that children are considerably more sensitive to the carcinogenic effects radiation. Image-guided surgery (IGS) uses pre-operative and intra-operative images to guide surgery or an interventional procedure. Central to every IGS system is a software application capable of processing and displaying patient images, registration between multiple coordinate systems, and interfacing with a tool tracking system. We have developed a novel image-guided surgery framework called Kit for Navigation by Image Focused Exploration (KNIFE). This software system serves as the core technology by which a system for reduction of radiation exposure to pediatric patients was developed. The bulk of the initial work in this research endevaour was the development of KNIFE which itself went through countless iterations before arriving at its current state as per the feature requirements established. Secondly, since this work involved the use of captured medical images and their use in an IGS software suite, a brief analysis of the physics behind the images was conducted. Through this aspect of the work, intrinsic parameters (principal point and focal point) of the fluoroscope were quantified using a 3D grid calibration phantom. A second grid phantom was traversed through the fluoroscopic imaging volume of II and flat panel based systems at 2 cm intervals building a scatter field of the volume to demonstrate pincushion and \u27S\u27 distortion in the images. Effects of projection distortion on the images was assessed by measuring the fiducial registration error (FRE) of each point used in two different registration techniques, where both methods utilized ordinary procrustes analysis but the second used a projection matrix built from the fluoroscopes calculated intrinsic parameters. A case study was performed to test whether the projection registration outperforms the rigid transform only. Using the knowledge generated were able to successfully design and complete mock clinical procedures using cardiac phantom models. These mock trials at the beginning of this work used a single point to represent catheter location but this was eventually replaced with a full shape model that offered numerous advantages. At the conclusion of this work a novel protocol for conducting IG ASD procedures was developed. Future work would involve the construction of novel EM tracked tools, phantom models for other vascular diseases and finally clinical integration and use