Analysis of CT imaging changes of psoas major muscles in patients with lumbar disc herniation mainly based on low back pain and lower limb pain

BackgroundThe study aimed to compare the area changes of CT (computed tomograghy) imaging of psoas major muscle (PM) in patients with lumbar disc herniation (LDH) mainly based on low back pain (LBP) and lower limb pain (LLP), and to analyze the correlation among them.MethodsWe retrospectively analyzed the lumbar CT imaging data of 120 patients with LDH and 60 healthy control people in our hospital from July 2017 to August 2019. They were divided into LBP group (60 cases), LLP group (60 cases) and healthy controls group (60 cases). According to the pain duration and pain degree, LBP group and LLP group were divided into three subgroups respectively. The maximum cross-sectional area (CSA) of PM and the CSA of L5 vertebral body were calculated by Image J software, and the ratio of them was the maximum CSA index of PM. The maximum CSA indices of PM among three groups and three subgroups were compared, respectively.ResultsThe baseline data among the three groups weren’t significantly different (P > 0.05), yet the maximum CSA index of PM did (P < 0.05). In the LBP group, the maximum CSA indices of PM among the three subgroups (short, medium and long) according to the pain duration were significantly different (P < 0.05), and those among the three subgroups (light, medium and heavy) according to pain degree did (P < 0.05). In the LLP group, the maximum CSA indices of PM among the three subgroups (short, medium and long) were compared, but there was not statistical difference among the three subgroups (P > 0.05). No statistical difference in terms of the maximum CSA indices of PM among the three subgroups (light, medium and heavy) was observed (P > 0.05).ConclusionThe atrophy and thinning of PM may be related to LDH. The correlation between the atrophy of PM and LBP was greater than that of LLP. The atrophy of PM in LDH patients with LBP increased with the prolongation of pain duration and aggravation of pain degree

Learn Single-horizon Disease Evolution for Predictive Generation of Post-therapeutic Neovascular Age-related Macular Degeneration

Most of the existing disease prediction methods in the field of medical image processing fall into two classes, namely image-to-category predictions and image-to-parameter predictions. Few works have focused on image-to-image predictions. Different from multi-horizon predictions in other fields, ophthalmologists prefer to show more confidence in single-horizon predictions due to the low tolerance of predictive risk. We propose a single-horizon disease evolution network (SHENet) to predictively generate post-therapeutic SD-OCT images by inputting pre-therapeutic SD-OCT images with neovascular age-related macular degeneration (nAMD). In SHENet, a feature encoder converts the input SD-OCT images to deep features, then a graph evolution module predicts the process of disease evolution in high-dimensional latent space and outputs the predicted deep features, and lastly, feature decoder recovers the predicted deep features to SD-OCT images. We further propose an evolution reinforcement module to ensure the effectiveness of disease evolution learning and obtain realistic SD-OCT images by adversarial training. SHENet is validated on 383 SD-OCT cubes of 22 nAMD patients based on three well-designed schemes based on the quantitative and qualitative evaluations. Compared with other generative methods, the generative SD-OCT images of SHENet have the highest image quality. Besides, SHENet achieves the best structure protection and content prediction. Qualitative evaluations also demonstrate that SHENet has a better visual effect than other methods. SHENet can generate post-therapeutic SD-OCT images with both high prediction performance and good image quality, which has great potential to help ophthalmologists forecast the therapeutic effect of nAMD

Label Adversarial Learning for Skeleton-level to Pixel-level Adjustable Vessel Segmentation

You can have your cake and eat it too. Microvessel segmentation in optical coherence tomography angiography (OCTA) images remains challenging. Skeleton-level segmentation shows clear topology but without diameter information, while pixel-level segmentation shows a clear caliber but low topology. To close this gap, we propose a novel label adversarial learning (LAL) for skeleton-level to pixel-level adjustable vessel segmentation. LAL mainly consists of two designs: a label adversarial loss and an embeddable adjustment layer. The label adversarial loss establishes an adversarial relationship between the two label supervisions, while the adjustment layer adjusts the network parameters to match the different adversarial weights. Such a design can efficiently capture the variation between the two supervisions, making the segmentation continuous and tunable. This continuous process allows us to recommend high-quality vessel segmentation with clear caliber and topology. Experimental results show that our results outperform manual annotations of current public datasets and conventional filtering effects. Furthermore, such a continuous process can also be used to generate an uncertainty map representing weak vessel boundaries and noise

Réglage de la pénétration capillaire dans les milieux poreux: combinaison des effets géométriques et d'évaporation

International audienceCapillary penetration of liquids in porous media is of great importance in many applications and the ability to tune such penetration processes is increasingly sought after. In general, liquid penetration can be retarded or restricted by the evaporation of volatile liquid at the surface of the porous media. Moreover, when capillary penetration occurs in a porous layer with non-uniform cross section, the penetration process can be accelerated or impeded by adjusting the section geometry. In this work, on the basis of Darcy's Law and mass conservation, a theoretical model of capillary penetration combining evaporation effects in two-dimensional homogeneous porous media of varying cross-section is developed and further examined by numerical simulations. The effects of sample geometry and liquid evaporation on capillary penetration are quantitatively analyzed. Results show that the penetration velocity is sensitive to the geometry of the porous layer, and can be tuned by varying the evaporation rate for a given geometry. Under given evaporation conditions, penetration is restricted to a limited region with a predictable boundary. Furthermore, we find that the inhibition of liquid penetration by evaporation can be offset by varying the geometry of the porous layer. In addition, the theoretical model is further extended to model the capillary flow in three-dimensional porous media, and the interplay of geometry and evaporation during the capillary flow process in 3D conditions is also investigated. The results obtained can be used for facilitating the design of porous structures, achieving tunable capillary penetration for practical applications in various fields.La pénétration capillaire de liquides dans des milieux poreux revêt une grande importance dans de nombreuses applications et la capacité de réglage de tels processus de pénétration est de plus en plus recherchée. En général, la pénétration de liquide peut être retardée ou limitée par l'évaporation de liquide volatil à la surface du support poreux. De plus, lorsque la pénétration capillaire se produit dans une couche poreuse de section transversale non uniforme, le processus de pénétration peut être accéléré ou empêché en ajustant la géométrie de la section. Dans ce travail, sur la base de la loi de Darcy et de la conservation de masse, un modèle théorique de pénétration capillaire combinant les effets d'évaporation dans des milieux poreux homogènes à deux dimensions de sections différentes est développé et examiné plus en détail par des simulations numériques. Les effets de la géométrie de l'échantillon et de l'évaporation du liquide sur la pénétration capillaire sont analysés de manière quantitative. Les résultats montrent que la vitesse de pénétration est sensible à la géométrie de la couche poreuse et peut être ajustée en faisant varier le taux d'évaporation pour une géométrie donnée. Dans des conditions d'évaporation données, la pénétration est limitée à une région limitée avec une limite prévisible. En outre, nous trouvons que l'inhibition de la pénétration du liquide par évaporation peut être compensée en faisant varier la géométrie de la couche poreuse. En outre, le modèle théorique est élargi pour modéliser l'écoulement capillaire dans des milieux poreux tridimensionnels, et les interactions entre la géométrie et l'évaporation pendant le processus d'écoulement capillaire dans des conditions 3D sont également étudiées. Les résultats obtenus peuvent être utilisés pour faciliter la conception de structures poreuses, en réalisant une pénétration capillaire ajustable pour des applications pratiques dans divers domaines

Modélisation multi-échelles des propriétés élastiques effectives de matériaux poreux remplis de fluide

International audienceFluid-filled porous materials are widely encountered in natural and artificial systems. A comprehensive understanding of the elastic behavior of such materials and its dependence on fluid diffusion is therefore of fundamental importance. In this work, a multiscale framework is developed to model the overall elastic response of fluid-filled porous materials. By utilizing a two-dimensional micromechanical model with porosity at two scales, the effects of fluid diffusion and the geometric arrangement of pores on the evolution of effective properties in fluid-filled porous materials are investigated. Initially, for a single-porosity model the effective elastic properties of the dry and fluid-filled porous materials with ordered pores are obtained theoretically by considering a geometrical factor, which is related to the distribution of pores in the matrix. Model predictions are validated by finite element simulations. By employing a double-porosity model, fluid diffusion from macro- to micro-scale pores driven by a pressure gradient is investigated, and the resulting time-dependent effective elastic properties are obtained for both constant pressure and constant injection rate conditions. It is found that the presence and diffusion of pressurized pore fluid significantly affect the elastic response of porous materials, and this must be considered when modeling such materials. It is expected that the proposed theoretical model will advance the understanding of the fluid-governed elastic response of porous materials with implications towards the analysis of geophysical, biological and artificial fluid-filled porous systems.https://doi.org/10.1016/j.ijsolstr.2018.11.028Les matériaux poreux remplis de fluide sont largement rencontrés dans les systèmes naturels et artificiels. Une compréhension globale du comportement élastique de tels matériaux et de sa dépendance à la diffusion de fluide revêt donc une importance fondamentale. Dans ce travail, un cadre multi-échelles est développé pour modéliser la réponse élastique globale des matériaux poreux remplis de fluide. En utilisant un modèle micromécanique bidimensionnel avec une porosité à deux échelles, on étudie les effets de la diffusion de fluide et la disposition géométrique des pores sur l'évolution des propriétés effectives dans les matériaux poreux remplis de fluide. Initialement, pour un modèle à une seule porosité, les propriétés élastiques effectives des matériaux poreux secs et remplis de fluide à pores ordonnés sont obtenues théoriquement en considérant un facteur géométrique, qui est lié à la distribution des pores dans la matrice. Les prévisions du modèle sont validées par des simulations par éléments finis. En utilisant un modèle à double porosité, on étudie la diffusion de fluide à partir de pores de macro à micro échelle, entraînés par un gradient de pression, et on obtient les propriétés élastiques effectives dépendantes du temps qui en résultent, à la fois pour des conditions de pression constante et de vitesse d'injection constante. On constate que la présence et la diffusion de fluide interstitiel sous pression affectent de manière significative la réponse élastique des matériaux poreux, ce qui doit être pris en compte lors de la modélisation de tels matériaux. Le modèle théorique proposé devrait permettre de mieux comprendre la réponse élastique des matériaux poreux régie par les fluides, avec des implications pour l'analyse de systèmes poreux remplis de fluides géophysiques, biologiques et artificiels

Une solution semi-analytique améliorée pour le stress aux encoches arrondies

International audienceIn order to investigate the brittle failure of keyhole notched components, the stress distribution at notch tips is studied numerically and theoretically. A semi-analytical formula is developed for the maximum notch-tip-stress, incorporating crack-tip-blunting, stress-concentration and stress-equilibrium. Stress distributions in notched plates are simulated by the finite-element method, showing improved accuracy of the formula relative to established solutions. Application of the developed equation to components containing U-notches and blunt V-notches, is explored, demonstrating its broad applicability. When combined with stress-based failure criteria, the semi-analytical model can be employed to assess brittle failure in notched components with significance toward fracture in heterogeneous materials.Afin d’étudier la défaillance fragile des composants à encoche en trou de serrure, la répartition des contraintes aux extrémités des entailles est étudiée numériquement et théoriquement. Une formule semi-analytique est élaborée pour la contrainte maximale en pointe, intégrant l’atténuation des fissures, la concentration en contrainte et l’équilibre en contrainte. Les distributions de contraintes dans les plaques à encoches sont simulées par la méthode des éléments finis, ce qui montre une précision améliorée de la formule par rapport aux solutions établies. L’application de l’équation développée aux composants contenant des encoches en U et des encoches en V contondantes est explorée, démontrant ainsi sa large applicabilité. Lorsqu'il est combiné à des critères de rupture fondés sur des contraintes, le modèle semi-analytique peut être utilisé pour évaluer la défaillance fragile de composants entaillés présentant une importance significative pour la rupture dans des matériaux hétérogènes

Two-dimensional modeling of the self-limiting oxidation in silicon and tungsten nanowires

AbstractSelf-limiting oxidation of nanowires has been previously described as a reaction- or diffusion-controlled process. In this letter, the concept of finite reactive region is introduced into a diffusion-controlled model, based upon which a two-dimensional cylindrical kinetics model is developed for the oxidation of silicon nanowires and is extended for tungsten. In the model, diffusivity is affected by the expansive oxidation reaction induced stress. The dependency of the oxidation upon curvature and temperature is modeled. Good agreement between the model predictions and available experimental data is obtained. The developed model serves to quantify the oxidation in two-dimensional nanostructures and is expected to facilitate their fabrication via thermal oxidation techniques