DYNAMIC MEASUREMENT OF THREE-DIMENSIONAL MOTION FROM SINGLE-PERSPECTIVE TWO-DIMENSIONAL RADIOGRAPHIC PROJECTIONS

The digital evolution of the x-ray imaging modality has spurred the development of numerous clinical and research tools. This work focuses on the design, development, and validation of dynamic radiographic imaging and registration techniques to address two distinct medical applications: tracking during image-guided interventions, and the measurement of musculoskeletal joint kinematics. Fluoroscopy is widely employed to provide intra-procedural image-guidance. However, its planar images provide limited information about the location of surgical tools and targets in three-dimensional space. To address this limitation, registration techniques, which extract three-dimensional tracking and image-guidance information from planar images, were developed and validated in vitro. The ability to accurately measure joint kinematics in vivo is an important tool in studying both normal joint function and pathologies associated with injury and disease, however it still remains a clinical challenge. A technique to measure joint kinematics from single-perspective x-ray projections was developed and validated in vitro, using clinically available radiography equipmen

Assessment of Normal Knee Kinematics Using High-Speed Stereo-Radiography System

The measurement of dynamic joint kinematics in vivo is important in order to understand the effects of joint injuries and diseases as well as for evaluating the treatment effectiveness. Quantification of knee motion is essential for assessment of joint function for diagnosis of pathology, such as tracking and progression of osteoarthritis and evaluation of outcome following conservative or surgical treatment. Total knee arthroplasty (TKA) is an invasive treatment for arthritic pain and functional disability and it is used for deformed joint replacement with implants in order to restore joint alignment. It is important to describe knee kinematics in healthy individuals for comparison in diagnosis of pathology and understanding treatment to restore normal function. However measuring the in vivo dynamic biomechanics in 6 degrees of freedom with an accuracy that is acceptable has been shown to be technically challenging. Skin marker based methods, commonly used in human movement analysis, are still prone to large errors produced by soft tissue artifacts. Thus, great deal of research has been done to obtain more accurate data of the knee joint by using other measuring techniques like dual plane fluoroscopy. The goal of this thesis is to use high-speed stereo radiography (HSSR) system for measuring joint kinematics in healthy older adults performing common movements of daily living such as straight walking and during higher demand activities of pivoting and step descending in order to establish a useful baseline for the envelope of healthy knee motion for subsequent comparison with patients with TKA. Prior to data collection, validation and calibration techniques as well as dose estimations were mandatory for the successful accomplishment of this study

Three-Dimensional Biplanar Reconstruction of the Scoliotic Spine for Standard Clinical Setup

Tese de Doutoramento. Engenharia Informática. Faculdade de Engenharia. Universidade do Porto. 201

Reconstruction 3D personnalisée de la colonne vertébrale à partir d'images radiographiques non-calibrées

Les systèmes de reconstruction stéréo-radiographique 3D -- La colonne vertébrale -- La scoliose idiopathique adolescente -- Évolution des systèmes de reconstruction 3D -- Filtres de rehaussement d'images -- Techniques de segmentation -- Les méthodes de calibrage -- Les méthodes de reconstruction 3D -- Problématique, hypothèses, objectifs et méthode générale -- Three-dimensional reconstruction of the scoliotic spine and pelvis from uncalibrated biplanar X-ray images -- A versatile 3D reconstruction system of the spine and pelvis for clinical assessment of spinal deformities -- Simulation experiments -- Clinical validation -- A three-dimensional retrospective analysis of the evolution of spinal instrumentation for the correction of adolescent idiopathic scoliosis -- Auto-calibrage d'un système à rayons-X à partir de primitives de haut niveau -- Segmentation de la colonne vertébrale -- Approche hiérarchique d'auto-calibrage d'un système d'acquisition à rayons-X -- Personalized 3D reconstruction of the scoliotic spine from hybrid statistical and X-ray image-based models -- Validation protocol

Intraoperative Endoscopic Augmented Reality in Third Ventriculostomy

In neurosurgery, as a result of the brain-shift, the preoperative patient models used as a intraoperative reference change. A meaningful use of the preoperative virtual models during the operation requires for a model update. The NEAR project, Neuroendoscopy towards Augmented Reality, describes a new camera calibration model for high distorted lenses and introduces the concept of active endoscopes endowed with with navigation, camera calibration, augmented reality and triangulation modules

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

A 3D computer assisted Orthopedic Surgery Planning approach based on planar radiography

Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Informática Médica)The main goal of this work consisted in develop a system to perform the 3D reconstruction of bone models from radiographic images. This system can be then integrated with a commercial software that performs pre-operative planning of orthopedic surgeries. The benefit of performing this 3D reconstruction from planar radiography is that this modality has some advantages over other modalities that perform this reconstruction directly, like CT and MRI. To develop the system it was used radiographic images of the femur obtained from medical image databases online. It was also used a generic model of the femur available in the online repository BEL. This generic model completes the information missing in the radiographic images. It was developed two methods to perform the 3D reconstruction through the deformation of the generic model, one uses triangulation of extracted edge points and the other don't. The first method was not successful, the final model had very low thickness, possibly because the triangulation process was not performed correctly. With the second method it was obtained a 3D bone model of the femur aligned with the radiographic images of the patient and with the same size as the patient's bone. However, the obtained model still needs some adjustment to coincide fully with reality. To perform this is necessary to enhance the deformation step of the model so that it will have the same shape as the patient's bone. The second method is more advantageous because it doesn't need the parameters of the x-ray imaging system. However, it's necessary to enhance the step deformation of this method so that the final model matches patient's anatomy.O principal objetivo deste trabalho consistiu em desenvolver um sistema capaz de realizar a reconstrução 3D de modelos ósseos a partir de imagens radiográficas. Este sistema pode posteriormente ser integrado num produto comercial que realiza o planeamento pré-operativo de cirurgias ortopédicas. O benefício de realizar esta reconstrução 3D a partir de radiografias está relacionado com o facto desta modalidade ter vantagens em relação às outras modalidades que fazem esta reconstrução diretamente, como as modalidades CT e MRI. Para desenvolver este sistema foram usadas imagens radiográficas do fémur obtidas através de bases de dados online de imagens médicas. Também foi usado um modelo genérico do fémur disponível no repositório online BEL. Este modelo genérico completa a informação que está em falta nas imagens radiográficas. Foram desenvolvidos dois métodos, que realizam a reconstrução 3D através da deformação do modelo genérico sendo que num é feita a triangulação de pontos dos contornos e noutro não. O primeiro método não foi bem sucedido, visto que o modelo final tinha uma espessura muito pequena, possivelmente devido ao facto do processo de triangulação não ter sido executado corretamente. Com o segundo método foi obtido um modelo 3D do fémur alinhado com as imagens radiográficas do paciente e com o mesmo tamanho do osso do paciente. No entanto, o modelo obtido carece ainda de alguma afinação de modo a coincidir na íntegra com a realidade. Para fazer isto é necessário melhorar o passo de deformação do modelo, para que este fique com a mesma forma do osso do paciente. O segundo método é mais vantajoso porque não necessita dos parâmetros dos sistema de raios- X. No entanto, é necessário melhorar o passo de deformação deste método para que o modelo final coincida com a anatomia do paciente

Towards markerless orthopaedic navigation with intuitive Optical See-through Head-mounted displays

The potential of image-guided orthopaedic navigation to improve surgical outcomes has been well-recognised during the last two decades. According to the tracked pose of target bone, the anatomical information and preoperative plans are updated and displayed to surgeons, so that they can follow the guidance to reach the goal with higher accuracy, efficiency and reproducibility. Despite their success, current orthopaedic navigation systems have two main limitations: for target tracking, artificial markers have to be drilled into the bone and calibrated manually to the bone, which introduces the risk of additional harm to patients and increases operating complexity; for guidance visualisation, surgeons have to shift their attention from the patient to an external 2D monitor, which is disruptive and can be mentally stressful. Motivated by these limitations, this thesis explores the development of an intuitive, compact and reliable navigation system for orthopaedic surgery. To this end, conventional marker-based tracking is replaced by a novel markerless tracking algorithm, and the 2D display is replaced by a 3D holographic Optical see-through (OST) Head-mounted display (HMD) precisely calibrated to a user's perspective. Our markerless tracking, facilitated by a commercial RGBD camera, is achieved through deep learning-based bone segmentation followed by real-time pose registration. For robust segmentation, a new network is designed and efficiently augmented by a synthetic dataset. Our segmentation network outperforms the state-of-the-art regarding occlusion-robustness, device-agnostic behaviour, and target generalisability. For reliable pose registration, a novel Bounded Iterative Closest Point (BICP) workflow is proposed. The improved markerless tracking can achieve a clinically acceptable error of 0.95 deg and 2.17 mm according to a phantom test. OST displays allow ubiquitous enrichment of perceived real world with contextually blended virtual aids through semi-transparent glasses. They have been recognised as a suitable visual tool for surgical assistance, since they do not hinder the surgeon's natural eyesight and require no attention shift or perspective conversion. The OST calibration is crucial to ensure locational-coherent surgical guidance. Current calibration methods are either human error-prone or hardly applicable to commercial devices. To this end, we propose an offline camera-based calibration method that is highly accurate yet easy to implement in commercial products, and an online alignment-based refinement that is user-centric and robust against user error. The proposed methods are proven to be superior to other similar State-of- the-art (SOTA)s regarding calibration convenience and display accuracy. Motivated by the ambition to develop the world's first markerless OST navigation system, we integrated the developed markerless tracking and calibration scheme into a complete navigation workflow designed for femur drilling tasks during knee replacement surgery. We verify the usability of our designed OST system with an experienced orthopaedic surgeon by a cadaver study. Our test validates the potential of the proposed markerless navigation system for surgical assistance, although further improvement is required for clinical acceptance.Open Acces

Augmented Reality Assistance for Surgical Interventions using Optical See-Through Head-Mounted Displays

Augmented Reality (AR) offers an interactive user experience via enhancing the real world environment with computer-generated visual cues and other perceptual information. It has been applied to different applications, e.g. manufacturing, entertainment and healthcare, through different AR media. An Optical See-Through Head-Mounted Display (OST-HMD) is a specialized hardware for AR, where the computer-generated graphics can be overlaid directly onto the user's normal vision via optical combiners. Using OST-HMD for surgical intervention has many potential perceptual advantages. As a novel concept, many technical and clinical challenges exist for OST-HMD-based AR to be clinically useful, which motivates the work presented in this thesis. From the technical aspects, we first investigate the display calibration of OST-HMD, which is an indispensable procedure to create accurate AR overlay. We propose various methods to reduce the user-related error, improve robustness of the calibration, and remodel the calibration as a 3D-3D registration problem. Secondly, we devise methods and develop hardware prototype to increase the user's visual acuity of both real and virtual content through OST-HMD, to aid them in tasks that require high visual acuity, e.g. dental procedures. Thirdly, we investigate the occlusion caused by the OST-HMD hardware, which limits the user's peripheral vision. We propose to use alternative indicators to remind the user of unattended environment motion. From the clinical perspective, we identified many clinical use cases where OST-HMD-based AR is potentially helpful, developed applications integrated with current clinical systems, and conducted proof-of-concept evaluations. We first present a "virtual monitor'' for image-guided surgery. It can replace real radiology monitors in the operating room with easier user control and more flexibility in positioning. We evaluated the "virtual monitor'' for simulated percutaneous spine procedures. Secondly, we developed ARssist, an application for the bedside assistant in robotic surgery. The assistant can see the robotic instruments and endoscope within the patient body with ARssist. We evaluated the efficiency, safety and ergonomics of the assistant during two typical tasks: instrument insertion and manipulation. The performance for inexperienced users is significantly improved with ARssist, and for experienced users, the system significantly enhanced their confidence level. Lastly, we developed ARAMIS, which utilizes real-time 3D reconstruction and visualization to aid the laparoscopic surgeon. It demonstrates the concept of "X-ray see-through'' surgery. Our preliminary evaluation validated the application via a peg transfer task, and also showed significant improvement in hand-eye coordination. Overall, we have demonstrated that OST-HMD based AR application provides ergonomic improvements, e.g. hand-eye coordination. In challenging situations or for novice users, the improvements in ergonomic factors lead to improvement in task performance. With continuous effort as a community, optical see-through augmented reality technology will be a useful interventional aid in the near future

Biomechanical Modeling and Characterization of the Postural Parameters in Adolescent Idiopathic Scoliosis

RÉSUMÉ La scoliose est une déformation 3D de la colonne vertébrale qui influence la morphologie et l'alignement de la colonne vertébrale, du bassin et de la cage thoracique. Bien que plusieurs paramètres soient introduits pour identifier et évaluer les courbes chez les sujets scoliotiques, la relation biomécanique entre la colonne vertébrale et le bassin ainsi que ses impacts sur la posture et l'équilibre général des sujets scoliotiques n’est pas encore élucidée. Le but de ce projet doctoral était d'examiner l'interaction spino-pelvienne en mesurant les paramètres biomécaniques chez les sujets atteints de scolioses idiopathiques adolescentes (SIA). La cinématique pelvienne, l'orientation spino-pelvienne relative et le chargement biomécanique lombo-sacré ont été examinés chez des sujets avec des courbures différentes. L’hypothèse que nous souhaitons vérifier est que l'interaction spino-pelvienne (au niveau des paramètres statiques, cinématiques et des chargements biomécaniques à l’interface entre le rachis et le bassin) est non seulement différente entre les SIA et les contrôles, mais varie aussi entre les sujets présentant différents types de scolioses. De plus, l'effet d’une instrumentation chirurgicale du rachis sur l’équilibre ainsi que sur l'interaction biomécanique spino-pelvienne a été étudié post opérativement. Donc, après avoir examiné la littérature pertinente, trois chapitres ont été consacrés pour examiner l'hypothèse générale de ce projet. Chaque chapitre aborde un aspect de l'interaction spino-pelvienne chez les sous-groupes scoliotiques et compare les résultats avec un groupe de contrôles de la même catégorie d'âge-sexe. Bien que l'orientation pelvienne entre les sujets SIA et le groupe contrôle était différente, il n'est pas vérifié dans quelle mesure l'orientation pelvienne et l'alignement spino-pelvien affectent la cinématique du bassin chez les sujets présentant différents types de courbures. Par la suite, l’interférence entre l'orientation du bassin et le mouvement spino-pelvien a été étudiée.----------ABSTRACT Scoliosis is a 3D spinal deformity which impacts the morphology and alignment of the spine, the pelvis, and the ribcage. Although several spinal parameters are introduced to identify and evaluate scoliotic curves, there is not much known about the biomechanical relationship between the spine and the pelvis and its impact on the overall posture and equilibrium of the scoliotic patients. The focus of this Ph.D. project was to investigate the spino-pelvic biomechanical interaction in adolescent idiopathic scoliosis (AIS) more closely. Spine and pelvic kinematic, relative spino-pelvic orientation in static, and lumbosacral biomechanical loading were investigated in subjects with different curve patterns. We hypothesized that spino-pelvic interaction is not only different between AIS and controls, but also varies between subjects with different scoliotic types in static, kinematic, and biomechanical loading. Furthermore the hypothetical effect of the spinal operation on equilibrating the spino-pelvic biomechanical interaction was tested postoperatively. Hence, after reviewing the pertinent literatures, 3 chapters were devoted to investigate the general hypothesis of this project. Each chapter tries to investigate one aspect of the spine and pelvis interaction in scoliotic subgroups and compares the results with an age-gender match group of controls. Although the pelvic alignment in the AIS group was different from the age-gender matched control group, it is not closely verified to what extent the pelvic orientation and the spino-pelvic alignment affect the pelvis kinematic in subjects with different curve types and subsequently its impact on the spino-pelvic movement is not determined. An experimental setup was designed to investigate the pelvic 3D motion during simple trunk movement in vivo