A semi-automatic computer-aided method for surgical template design

This paper presents a generalized integrated framework of semi-automatic surgical template design. Several algorithms were implemented including the mesh segmentation, offset surface generation, collision detection, ruled surface generation, etc., and a special software named TemDesigner was developed. With a simple user interface, a customized template can be semi- automatically designed according to the preoperative plan. Firstly, mesh segmentation with signed scalar of vertex is utilized to partition the inner surface from the input surface mesh based on the indicated point loop. Then, the offset surface of the inner surface is obtained through contouring the distance field of the inner surface, and segmented to generate the outer surface. Ruled surface is employed to connect inner and outer surfaces. Finally, drilling tubes are generated according to the preoperative plan through collision detection and merging. It has been applied to the template design for various kinds of surgeries, including oral implantology, cervical pedicle screw insertion, iliosacral screw insertion and osteotomy, demonstrating the efficiency, functionality and generality of our method.Comment: 18 pages, 16 figures, 2 tables, 36 reference

Automatic Lumbar Vertebral Identification Using Surface-Based Registration

AbstractThis work proposes the use of surface-based registration to automatically select a particular vertebra of interest during surgery. Manual selection of the correct vertebra can be a challenging task, especially for closed-back, minimally invasive procedures. Our method uses shape variations that exist among lumbar vertebrae to automatically determine the portion of the spinal column surface that correctly matches a set of physical vertebral points. In our experiments, we register vertebral points representing posterior elements of a single vertebra in physical space to spinal column surfaces extracted from computed tomography images of multiple vertebrae. After registering the set of physical points to each vertebral surface that is a potential match, we then compute the standard deviation of the surface error for each registration trial. The registration that corresponds to the lowest standard deviation designates the correct match. We have performed our current experiments on two plastic spine phantoms and two patients

A multi-center milestone study of clinical vertebral CT segmentation

A multiple center milestone study of clinical vertebra segmentation is presented in this paper. Vertebra segmentation is a fundamental step for spinal image analysis and intervention. The first half of the study was conducted in the spine segmentation challenge in 2014 International Conference on Medical Image Computing and Computer Assisted Intervention (MICCAI) Workshop on Computational Spine Imaging (CSI 2014). The objective was to evaluate the performance of several state-of-the-art vertebra segmentation algorithms on computed tomography (CT) scans using ten training and five testing dataset, all healthy cases; the second half of the study was conducted after the challenge, where additional 5 abnormal cases are used for testing to evaluate the performance under abnormal cases. Dice coefficients and absolute surface distances were used as evaluation metrics. Segmentation of each vertebra as a single geometric unit, as well as separate segmentation of vertebra substructures, was evaluated. Five teams participated in the comparative study. The top performers in the study achieved Dice coefficient of 0.93 in the upper thoracic, 0.95 in the lower thoracic and 0.96 in the lumbar spine for healthy cases, and 0.88 in the upper thoracic, 0.89 in the lower thoracic and 0.92 in the lumbar spine for osteoporotic and fractured cases. The strengths and weaknesses of each method as well as future suggestion for improvement are discussed. This is the first multi-center comparative study for vertebra segmentation methods, which will provide an up-to-date performance milestone for the fast growing spinal image analysis and intervention

Accuracy of 3D printed spine models for pre-surgical planning of complex adolescent idiopathic scoliosis (AIS) in spinal surgeries: a case series

Adolescent idiopathic scoliosis (AIS) is a noticeable spinal deformity in both adult and adolescent population. In majority of the cases, the gold standard of treatment is surgical intervention. Technological advancements in medical imaging and 3D printing have revolutionised the surgical planning and intraoperative decision making for surgeons in spinal surgery. However, its applicability for planning complex spinal surgeries is poorly documented with human subjects. The objective of this study is to evaluate the accuracy of 3D printed models for complex spinal deformities based on Cobb angles between 40° to 95°.This is a retrospective cohort study where, five CT scans of the patients with AIS were segmented and 3D printed for evaluating the accuracy. Consideration was given to the Inter-patient and acquisition apparatus variability of the CT-scan dataset to understand the effect on trueness and accuracy of the developed CAD models. The developed anatomical models were re-scanned for analysing quantitative surface deviation to assess the accuracy of 3D printed spinal models. Results show that the average of the root mean square error (RMSE) between the 3DP models and virtual models developed using CT scan of mean surface deviations for the five 3d printed models was found to be 0.5§0.07 mm. Based on the RMSE, it can be concluded that 3D printing based workflow is accurate enough to be used for presurgical planning for complex adolescent spinal deformities. Image acquisition and post processing parameters, type of 3D printing technology plays key role in acquiring required accuracy for surgical applications

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

Mechanical and morphometric characterization of cancellous bone

[EN] Bone fracture is a social health problem of increasing magnitude because of its prevalence in aged population due to osteoporosis. Bone quality is often characterized by bone mineral density (BMD) measured at cancellous bone regions using dual-energy X-ray absorptiometry (DXA). However, BMD alone cannot predict several cases because not only density is important, but also microstructure plays an important role in cancellous bone strength. The mechanical properties can be used as indicators of bone integrity as a function of age, disease or treatment. Therefore, cancellous bone fracture characterization and its relationship to microstructure has not been completely solved in the literature and is relevant to improve fracture prediction. In this thesis, we aim at characterizing cancellous bone morphometry and mechanical behavior. Morphometry is estimated through the analysis of micro-computed tomography (micro-CT) images of vertebral cancellous bone specimens. With regards to the mechanical behavior, we calculate elastic, yield and failure properties at the apparent and tissue levels. To determine them, we followed different approaches: compression tests, finite element models and micro-CT phantoms. We have developed finite element models that reproduce the elastic and failure response of cancellous bone under compression conditions. We modeled failure as a combination of continuum damage mechanics and the element deletion technique. The numerical models permitted to estimate elastic and failure properties. Failure properties were consistent with results reported in the literature. Specifically, our results revealed that yield strain is relatively constant (0.7 %) over a range of apparent densities, while failure strain presents a wider range of variation. A single strain parameter (equivalent strain) was found as an accurate descriptor of cancellous bone compression failure. Image-based numerical models usually need for the action of a technician to segment the images. Therefore, we studied the sensitivity to variations of the segmentation threshold on the morphometry and the elastic properties of vertebral cancellous bone specimens of different bone volume fractions. The apparent modulus is highly sensitive to the segmentation threshold. We report variations between 45 and 120 % for a ± 15 % threshold variation. Other parameters, such as BS/BV, BS/TV, Tb.Sp, Tb.N, Conn.D and fractal dimension were influenced significantly. Digital image correlation (DIC) was applied to images taken during compression testing to analyze displacement fields at failure and characterize them. Some variables were explored to describe failure and a study is done about how DIC parameters influence the strain field obtained. Facet and step sizes have a relevant effect on the failure strain estimation, and an increment of both parameters reduces the strain estimation up to 40 %. Besides, several parameters combination led to correct failure pattern detection, so values reported in the literature should be referred to the parameters used. Furthermore, we explored if cancellous bone microstructure acts (non-speckle/texture approach) as a proper pattern to calculate displacements using DIC technique. As regards relationships between microstructure and mechanics, single and multiple parameter analysis were performed to assess the morphometric variables that control the explanation of mechanical properties variation. Bone volume fraction (BV/TV), bone surface to volume ratio (BS/BV), mean trabecular thickness (Tb.Th) and fractal dimension (D) presented the best linear correlations to the elastic properties, while both the yield and failure strains did not show correlation to any morphometric parameter. The regressions obtained permit to estimate those mechanical properties that describe the state of a specimen.[ES] Las fracturas óseas constituyen un problema social de salud con magnitud creciente por su prevalencia en la población de edad avanzada debido a la osteoporosis. La calidad del hueso suele caracterizarse mediante la estimación de la densidad mineral ósea (DMO) en regiones de hueso trabecular, utilizando absorciometría de rayos X de energía dual (DXA). No obstante, la DMO por si sola no es capaz de predecir numerosos casos de fractura porque no solo importa la pérdida de densidad, sino que la microestructura también tiene un papel principal en la resistencia del hueso. Las propiedades mecánicas del hueso pueden usarse como indicadores de su integridad en función de la edad, enfermedad o tratamiento. Por lo tanto, la caracterización de la fractura de hueso trabecular y su relación con la microestructura no se ha resuelto de forma completa en la literatura y es relevante para mejorar las predicciones de fractura. En esta tesis, nuestro principal objetivo es caracterizar la morfometría y el comportamiento mecánico del hueso trabecular. Estimamos la morfometría a través del análisis de imágenes obtenidas por micro tomografía computerizada (micro-CT) de muestras de hueso trabecular vertebral de cerdo. Respecto al comportamiento mecánico, calculamos propiedades elásticas, de plasticidad y fractura a escala aparente y de tejido. Para determinar esas propiedades, hemos seguido diferentes procedimientos: ensayos a compresión, modelos de elementos finitos y fantomas de calibración micro-CT. Los modelos de elementos finitos desarrollados reproducen la respuesta elástica y de fallo bajo condiciones de compresión en hueso trabecular, modelando el fallo como combinación de mecánica del daño contínuo y la técnica de eliminación de elementos. Los modelos numéricos desarrollados han permitido estimar propiedades elásticas y de fallo. En concreto, las deformaciones de inicio de fallo estimadas son relativamente constantes para las muestras analizadas (0.7 %), mientras que las deformaciones últimas de fallo presentan un rango de variación mayor. Por otro lado, encontramos que la deformación equivalente es el descriptor más preciso del fallo a compresión del hueso trabecular. Normalmente, los modelos numéricos basados en imágenes suelen necesitar la acción de un técnico para segmentar las imágenes. En este sentido, estudiamos la sensibilidad de la morfometría y la estimación de propiedades elásticas ante variaciones en el umbral de segmentación en muestras con distinta fracción en volumen. Hemos obtenido que la rigidez aparente es muy sensible a cambios en el umbral de segmentación, con variaciones entre 45 y 120 % para una variación de ± 15 % del umbral de segmentación. Otros parámetros, como BS/BV, BS/TV, Tb.Sp, Tb.N, Conn.D y la dimensión fractal se ven afectados significativamente. Por otro lado, hemos aplicado la técnica correlación digital por imagen (DIC) para caracterizar campos de desplazamientos en el fallo a compresión del hueso trabecular, a partir del análisis de imágenes tomadas durante el ensayo de las muestras. Además, estudiamos la influencia de algunos parámetros de la técnica DIC en el campo de deformaciones obtenido. También, hemos explorado la aplicación DIC sin el uso de moteado, utilizando como patrón de reconocimiento la propia microestructura trabecular. En relación al estudio de la influencia de la microestructura en la respuesta mecánica, hemos calculado correlaciones de uno y varios parámetros para analizar qué variables morfométricas explican la variación de las propiedades mecánicas. La fracción en volumen de hueso (BV/TV), la relación entre el área y el volumen de hueso (BS/BV), el espesor trabecular medio (Tb.Th) y la dimensión fractal (D) presentan las mejores correlaciones lineales respecto a las propiedades elásticas, mientras que las deformaciones de inicio de plasticidad y fractura no mostraron correlación con ningún parámetro morfométrico.[CA] Les fractures òssies constitueixen un problema social de salut amb magnitud creixent per la seua prevalença en la població d'edat avançada a causa de l'osteoporosi. La qualitat de l'os sol caracteritzar-se mitjançant l'estimació de la densitat mineral òssia (DMO) en regions d'os trabecular, utilitzant absorciometria de raigs X d'energia dual (DXA). No obstant això, la DMO per si sola no és capaç de predir nombrosos casos de fractura perquè no sols importa la pèrdua de densitat, sinó que la microestructura també té un paper principal en la resistència de l'os. Les propietats mecàniques de l'os poden usar-se com a indicadors de la seua integritat en funció de l'edat, malaltia o tractament. Per tant, la caracterització de la fractura d'os trabecular i la seua relació amb la microestructura no s'ha resolt de manera completa en la literatura i és rellevant per a millorar les prediccions de fractura. En aquesta tesi, el nostre principal objectiu és caracteritzar la morfometria i el comportament mecànic de l'os trabecular. Estimem la morfometria a través de l'anàlisi d'imatges obtingudes per micro tomografia automatitzada (micro-CT) de mostres d'os trabecular vertebral de porc. Respecte al comportament mecànic, calculem propietats elàstiques, de plasticitat i fractura a escala aparent i de teixit. Per a determinar aqueixes propietats, hem seguit diferents procediments: assajos a compressió, models d'elements finits i fantomas de calibratge micro-CT. Hem desenvolupat models d'elements finits que reprodueixen la resposta elàstica i de fallada sota condicions de compressió en os trabecular, modelant la fallada com a combinació de mecànica del dany continu i la tècnica d'eliminació d'elements. Els models numèrics desenvolupats han permés estimar propietats elàstiques i de fallada. Les nostres estimacions respecte a propietats de fallada són consistents amb valors reportats en la literatura. En concret, les deformacions d'inici de fallada estimades són relativament constants per a les mostres analitzades (0.7 %), mentre que les deformacions últimes de fallada presenten un rang de variació major. D'altra banda, trobem que la deformació equivalent és el descriptor més precís de la fallada a compressió de l'os trabecular. Els models numèrics basats en imatges solen necessitar l'acció d'un tècnic per a segmentar les imatges. En aquest sentit, estudiem la sensibilitat de la morfometria i l'estimació de propietats elàstiques davant variacions en el llindar de segmentació en mostres amb diferent fracció en volum. Hem obtingut que la rigidesa aparent és molt sensible a canvis en el llindar de segmentació, amb variacions entre 45 i 120 % per a una variació de ± 15 % del llindar de segmentació. Altres paràmetres, com BS/BV, BS/TV, Tb.Sp, Tb.N, Conn.D i la dimensió fractal es veuen afectats significativament. D'altra banda, hem aplicat la tècnica correlació digital per imatge (DIC) per a caracteritzar camps de desplaçaments en la fallada a compressió de l'os trabecular, a partir de l'anàlisi d'imatges preses durant l'assaig de les mostres. A més, estudiem la influència d'alguns paràmetres de la tècnica DIC en el camp de deformacions obtingut. També, hem explorat l'aplicació DIC sense l'ús de clapejat, utilitzant com a patró de reconeixement la pròpia microestructura trabecular. En relació a l'estudi de la influència de la microestructura en la resposta mecànica, hem calculat correlacions d'un i diversos paràmetres per a analitzar quines variables morfomètriques expliquen la variació de les propietats mecàniques. La fracció en volum d'os (BV/TV), la relació entre l'àrea i el volum d'os (BS/BV), la espessor trabecular mitjà (Tb.th) i la dimensió fractal (D) presenten les millors correlacions lineals respecte a les propietats elàstiques, mentre que les deformacions d'inici de plasticitat i fractura no van mostrar correlació amb cap paràmetre morfomètric.Belda González, R. (2020). Mechanical and morphometric characterization of cancellous bone [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149376TESI

Advanced Applications of Rapid Prototyping Technology in Modern Engineering

Rapid prototyping (RP) technology has been widely known and appreciated due to its flexible and customized manufacturing capabilities. The widely studied RP techniques include stereolithography apparatus (SLA), selective laser sintering (SLS), three-dimensional printing (3DP), fused deposition modeling (FDM), 3D plotting, solid ground curing (SGC), multiphase jet solidification (MJS), laminated object manufacturing (LOM). Different techniques are associated with different materials and/or processing principles and thus are devoted to specific applications. RP technology has no longer been only for prototype building rather has been extended for real industrial manufacturing solutions. Today, the RP technology has contributed to almost all engineering areas that include mechanical, materials, industrial, aerospace, electrical and most recently biomedical engineering. This book aims to present the advanced development of RP technologies in various engineering areas as the solutions to the real world engineering problems

Méthode de mesure automatique intraopératoire des déformations du rachis scoliotique

RÉSUMÉ La scoliose idiopathique de l'adolescence est une pathologie complexe et évolutive entraînant une déformation tridimensionnelle du rachis, de la cage thoracique et du bassin. Cette pathologie affecte 2 à 4% de la population adolescente. Dans le cas de scolioses sévères, un traitement chirurgical est recommandé. L’imagerie radiographique est la technique la plus répandue pour le diagnostic et le suivi des effets de cette pathologie. De plus, des outils de reconstruction 3D du rachis à partir de radiographies du patient sont actuellement disponibles avant la chirurgie pour permettre une caractérisation bi- et tridimensionnelle des déformations scoliotiques ainsi que la planification des manoeuvres d'instrumentation. Les modèles 3D préopératoires ne sont pas directement utilisables pendant la chirurgie puisqu'il y existe un changement des courbures scoliotiques dû à la position allongée, à l'exposition chirurgicale et à l'anesthésie. Plusieurs systèmes de suivi ont été testés pour suivre le changement de forme du rachis et le mouvement des vertèbres en intraopératoire : mécaniques, optoélectroniques, électromagnétiques, ultrasons, radiographiques. Ces systèmes permettent de détecter la position des vertèbres pendant la chirurgie et peuvent être utilisés pour la mise à jour de modèles 3D préopératoires. Pour ce faire, ils requièrent l'installation de marqueurs sur les vertèbres ou l'identification manuelle de points anatomiques pendant la chirurgie, ce qui peut interférer avec la procédure chirurgicale. Ainsi, des systèmes d'imagerie et de navigation intraopératoires sont actuellement disponibles pour visualiser les déformations 3D du rachis et guider les manoeuvres d'instrumentation de façon sûre et précise. Cependant, à partir de ces systèmes, il n'est pas encore possible de quantifier en intraopératoire les déformations scoliotiques et la correction résultant des manoeuvres d'instrumentation. Ce projet de maîtrise visait à développer une technique permettant la mesure intraopératoire automatique des déformations scoliotiques afin de fournir au chirurgien des données quantitatives exploitables pour évaluer et améliorer la stratégie chirurgicale. Globalement, le calcul des déformations scoliotiques 3D a été effectué grâce à la mise à jour d'un modèle géométrique préopératoire à partir d'images fluoroscopiques 3D intraopératoires. De façon plus précise, un modèle géométrique préopératoire a été construit à partir de 28 repères anatomiques vertébraux identifiés manuellement par un opérateur sur des radiographies biplanaires en position érigée avant la chirurgie. Ces points ont été utilisés pour obtenir un modèle----------ABSTRACT Adolescent idiopathic scoliosis (AIS) is a complex and progressive pathology leading to threedimensional deformities of the spine, rib cage and pelvis. This pathology affects 2 to 4% of the adolescent population. In the case of severe scoliosis, a surgical treatment is required. Radiographic imaging is mostly used for the diagnosis and the monitoring of scoliosis. 3D reconstruction of the spine from patient’s radiographs is currently available to enable the twoand three-dimensional characterization of scoliotic deformities and planning of the instrumentation maneuvers. The 3D preoperative models can’t be directly used during surgery since there is a change in the scoliotic curvature caused by the prone positioning, the surgical exposure and the anesthesia. Several tracking systems have been tested to monitor the spinal shape changes and follow the intraoperative motion of the vertebrae: optoelectronics or electromagnetics systems, ultrasounds, radiographs. These systems enable the tracking of the intraoperative positioning of the vertebrae, and can be used to update 3D preoperative models. This requires the installation of external markers on vertebrae or the manual identification of anatomic points during surgery, which can interfere with the surgical procedure. Imaging and navigation systems are then currently available to visualize the 3D deformities of the spine and to safely and precisely guide the instrumentation maneuvers. Nevertheless, these systems do not enable the quantification of the intraoperative scoliotic deformities and the correction resulting from instrumentation maneuvers. This project aimed to develop a technique that enables the automatic intraoperative measurement of the scoliotic deformities, in order to provide the surgeon with quantitative feedback to evaluate and improve the surgical strategy. The 3D scoliotic deformities were computed by registering a preoperative geometric model with intraoperative 3D fluoroscopic images of the spine. More precisely, a preoperative geometric model was constructed from 28 vertebral landmarks manually identified by an operator on biplanar radiographs acquired preoperatively in standing position. These landmarks were used to obtain a surface model of each vertebra though a dual kriging interpolation technique. The intraoperative model was computed by the registration between this preoperative geometric model and the intraoperative data, composed of a voxelized model obtained from 3D fluoroscopic images. Each vertebra of the voxelized model was segmented and manually identified on intraoperative 3D fluoroscopic images. A rigid registratio