Reconstruction 3D biplanaire non supervisée de la colonne vertébrale et de la cage thoracique scoliotiques par modèles statistiques

Cette thèse présente trois approches statistiques pour la reconstruction 3D de la colonne vertébrale et de la cage thoracique scoliotiques à partir de deux images radiographiques conventionnelles. Globalement, les méthodes sont basées sur l'utilisation de contours de vertèbres ou des côtes détectées dans deux images radiographiques et une connaissance géométrique a priori de nature statistique de chaque élément. La reconstruction est formulée comme un problème de minimisation de fonctions d'énergie résolues par des méthodes d'optimisation. Pour la colonne vertébrale, les méthodes sont validées par comparaison avec des reconstructions de 57 vertèbres scoliotiques reconstruites à partir d'images tomodensitométriques. Plusieurs méthodes ont été proposées afin de raffiner les solutions obtenues et de rendre les méthodes non supervisées

A Novel Method for the 3-D Reconstruction of Scoliotic Ribs From Frontal and Lateral Radiographs

Among the external manifestations of scoliosis, the rib hump, which is associated with the ribs' deformities and rotations, constitutes the most disturbing aspect of the scoliotic deformity for patients. A personalized 3-D model of the rib cage is important for a better evaluation of the deformity, and hence, a better treatment planning. A novel method for the 3-D reconstruction of the rib cage, based only on two standard radiographs, is proposed in this paper. For each rib, two points are extrapolated from the reconstructed spine, and three points are reconstructed by stereo radiography. The reconstruction is then refined using a surface approximation. The method was evaluated using clinical data of 13 patients with scoliosis. A comparison was conducted between the reconstructions obtained with the proposed method and those obtained by using a previous reconstruction method based on two frontal radiographs. A first comparison criterion was the distances between the reconstructed ribs and the surface topography of the trunk, considered as the reference modality. The correlation between ribs axial rotation and back surface rotation was also evaluated. The proposed method successfully reconstructed the ribs of the 6th-12th thoracic levels. The evaluation results showed that the 3-D configuration of the new rib reconstructions is more consistent with the surface topography and provides more accurate measurements of ribs axial rotation.Natural Sciences and Engineering Research Council of Canada and MENTOR, a strategic training program of the Canadian Institutes of Health Research

Intervertebral disc characterization by shear wave elastography: An in vitro preliminary study.

Published onlineJOURNAL ARTICLEAuthor's accepted (post-print) manuscriptThe final version of record is available at http://dx.doi.org/10.1177/0954411914540279Patient-specific numerical simulation of the spine is a useful tool both in clinic and research. While geometrical personalization of the spine is no more an issue, thanks to recent technological advances, non-invasive personalization of soft tissue's mechanical properties remains a challenge. Ultrasound elastography is a relatively recent measurement technique allowing the evaluation of soft tissue's elastic modulus through the measurement of shear wave speed. The aim of this study was to determine the feasibility of elastographic measurements in intervertebral disc. An in vitro approach was chosen to test the hypothesis that shear wave speed can be used to evaluate intervertebral disc mechanical properties and to assess measurement repeatability. In total, 11 oxtail intervertebral discs were tested in compression to determine their stiffness and apparent elastic modulus at rest and at 400 N. Elastographic measurements were performed in these two conditions and compared to these mechanical parameters. The protocol was repeated six times to determine elastographic measurement repeatability. Average shear wave speed over all samples was 5.3 ± 1.0 m/s, with a repeatability of 7% at rest and 4.6% at 400 N; stiffness and apparent elastic modulus were 266.3 ± 70.5 N/mm and 5.4 ± 1.1 MPa at rest, respectively, while at 400 N they were 781.0 ± 153.8 N/mm and 13.2 ± 2.4 MPa, respectively. Correlations were found between elastographic measurements and intervertebral disc mechanical properties; these preliminary results are promising for further in vivo application.ParisTech BiomecAM chair programProteorParisTechYves Cotrel Foundation

Intervertebral disc characterization by shear wave elastography: an in-vitro preliminary study

Patient-specific numerical simulation of the spine is a useful tool both in clinic and research. While geometrical personalization of the spine is no more an issue, thanks to recent technological advances, non-invasive personalization of soft tissue’s mechanical properties remains a challenge. Ultrasound elastography is a relatively recent measurement technique allowing the evaluation of soft tissue’s elastic modulus through the measurement of shear wave speed (SWS). The aim of this study was to determine the feasibility of elastographic measurements in intervertebral disc (IVD). An in-vitro approach was chosen to test the hypothesis that SWS can be used to evaluate IVD mechanical properties and to assess measurement repeatability. Eleven oxtail IVDs were tested in compression to determine their stiffness and apparent elastic modulus at rest and at 400 N. Elastographic measurements were performed in these two conditions and compared to these mechanical parameters. The protocol was repeated six times to determine elastographic measurement repeatability. Average SWS over all samples was 5.3 ± 1.0 m/s, with a repeatability of 7 % at rest and 4.6 % at 400 N; stiffness and apparent elastic modulus were 266.3 ± 70.5 N/mm and 5.4 ± 1.1 MPa at rest, respectively, while at 400 N they were 781.0 ± 153.8 N/mm and 13.2 ± 2.4 MPa. Correlations were found between elastographic measurements and IVD mechanical properties; these preliminary results are promising for further in-vivo application.The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling for funding (with the support of Proteor, ParisTech and Yves Cotrel Foundations)

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

3D registration of MR and X-ray spine images using an articulated model

Présentation: Cet article a été publié dans le journal : Computerised medical imaging and graphics (CMIG). Le but de cet article est de recaler les vertèbres extraites à partir d’images RM avec des vertèbres extraites à partir d’images RX pour des patients scoliotiques, en tenant compte des déformations non-rigides due au changement de posture entre ces deux modalités. À ces fins, une méthode de recalage à l’aide d’un modèle articulé est proposée. Cette méthode a été comparée avec un recalage rigide en calculant l’erreur sur des points de repère, ainsi qu’en calculant la différence entre l’angle de Cobb avant et après recalage. Une validation additionelle de la méthode de recalage présentée ici se trouve dans l’annexe A. Ce travail servira de première étape dans la fusion des images RM, RX et TP du tronc complet. Donc, cet article vérifie l’hypothèse 1 décrite dans la section 3.2.1.Abstract This paper presents a magnetic resonance image (MRI)/X-ray spine registration method that compensates for the change in the curvature of the spine between standing and prone positions for scoliotic patients. MRIs in prone position and X-rays in standing position are acquired for 14 patients with scoliosis. The 3D reconstructions of the spine are then aligned using an articulated model which calculates intervertebral transformations. Results show significant decrease in regis- tration error when the proposed articulated model is compared with rigid registration. The method can be used as a basis for full body MRI/X-ray registration incorporating soft tissues for surgical simulation.Canadian Institute of Health Research (CIHR

Statistical atlas based registration and planning for ablating bone tumors in minimally invasive interventions

Bone tumor ablation has been a viable treatment in a minimally invasive way compared with surgical resections. In this paper, two key challenges in the computer-Assisted bone tumor ablation have been addressed: 1) establishing the spatial transformation of patient's tumor with respect to a global map of the patient using a minimum number of intra-operative images and 2) optimal treatment planning for large tumors. Statistical atlas is employed to construct the global reference map. The atlas is deformably registered to a pair of intra-operative fluoroscopy images, constructing a patient-specific model, in order to reduce the radiation exposure to the sensitive patients such as pregnant and infants. The optimal treatment planning system incorporates clinical constraints on ablations and trajectories using a multiple objective optimization, which obtains optimal trajectory planning and ablation coverage using integer programming. The proposed system is presented and validated by experiments. © 2012 IEEE.published_or_final_versio

Patient Positioning for Surgeries of the Spine : How Does it Impact Spinal Geometry and How Can it be Exploited to Improve Surgical Procedures

RÉSUMÉ Les cas les plus graves de déformation rachidienne, telles que la scoliose, nécessitent une intervention chirurgicale afin de traiter les symptômes et de réaligner la colonne vertébrale. Au cours de l'intervention chirurgicale, les patients sont habituellement maintenus dans une position en décubitus ventral et une instrumentation est utilisée pour corriger et fixer la géométrie de la colonne. Il a été démontré que le positionnement des patients sur des cadres chirurgicaux a un impact sur la géométrie rachidienne, mais ceci n'est pas exploité afin de faciliter et améliorer les procédures chirurgicales. Les cadres disponibles commercialement ont des capacités limitées de positionnement du patient qui puisse être modifiable durant l'intervention. Aussi, afin d‟exploiter éventuellement les diverses possibilités de positionnement, on doit connaître l‟impact de ces positions sur la modulation de la géométrie de la colonne vertébrale du patient opéré. Ce projet a été effectué en parallèle avec la conception et la construction d'un nouveau cadre de positionnement multifonctionnel (MFPF) pour les chirurgies du rachis qui permet le positionnement des membres inférieurs ainsi que le déplacement vertical du thorax. Le MFPF lui-même était une combinaison de deux cadres précédents permettant le positionnement chirurgical: le DPF (permettant le réglage de coussins sur le tronc et l'application de forces correctives) et le "leg positionner" (permettant la flexion et l'extension des membres inférieurs). La modélisation par éléments finis (MEF) a été utilisée pour étudier le positionnement de patient sur le DPF. Les objectifs spécifiques de ce projet étaient: 1) d'adapter et développer une MEF de la colonne vertébrale, cage thoracique, bassin, et des membres inférieurs qui soit capable de simuler les effets géométriques sur la colonne vertébrale résultant du positionnement en décubitus ventral et de l‟ajustement des capacités de positionnement du MFPF; 2) effectuer des essais expérimentaux sur le positionnement en décubitus ventral et les capacités de positionnement du MFPF et utiliser les résultats pour valider le MFF; 3) exploiter le MEF pour développer de nouvelles possibilités de positionnement sur le MFPF permettant de moduler la géométrie de la colonne vertébrale et évaluer ces nouvelles positions expérimentalement avec des accessoires construit pour le MFPF; et 4) exploiter la MEF afin d'étudier l'impact de la combinaison des----------ABSTRACT The most severe cases of spinal deformity, such as scoliosis, require surgical intervention in order to treat symptoms and re-align the spine. During surgical procedures, patients are typically kept in the prone position while surgical instrumentation is utilized to manipulate and fix spinal geometry. Patient positioning on surgical frames has been shown to have an impact on spinal geometry which can be exploited in order to facilitate and improve upon surgical procedures. Current commercial surgical frames have no or limited patient positioning capabilities. In order to best take advantage of a surgical frame‟s positioning capabilities, knowledge must be gained on how they will impact a given patient‟s spinal geometry. This project was done in parallel with the design and construction of a new Multi-Functional Positioning Frame (MFPF) for spinal surgeries which allowed for lower limb positioning and thoracic vertical displacement. The MFPF itself was a combination of two previously developed surgical positioning devices: the Dynamic Positioning Frame (DPF) (allowing thoracic cushion adjustment and corrective force application) and the “leg positioner” (allowing hip flexion and extension). Finite element modeling (FEM) was previously used to study patient positioning on the DPF. The global objective of this thesis was to study how patient positioning on a frame can be used in order to improve scoliosis instrumentation procedures through the intra-operative manipulation of spinal geometry. The specific objectives of this project were: 1) adapt and develop a FEM of the spine, thoracic cage, pelvis, and adjacent structures that is able to simulate the geometric effects on the spine resulting from prone positioning and feature adjustment on the MFPF; 2) experimentally test the impact of prone positioning and feature adjustment on the MFPF and utilize the results to validate the FEM; 3) exploit the FEM in order to study additional surgical positions allowing modification of spinal geometrical parameters not possible on the original MFPF design and experimentally assess these new positions using proof of concept features constructed for the MFPF; and 4) exploit the FEM in order to study the impact of combined MFPF positioning parameters on the geometry of the spine (especially the leg positioning and thoracic components) including developing a method allowing for individual an