Self-Supervised Learning for Cardiac MR Image Segmentation by Anatomical Position Prediction

In the recent years, convolutional neural networks have transformed the field of medical image analysis due to their capacity to learn discriminative image features for a variety of classification and regression tasks. However, successfully learning these features requires a large amount of manually annotated data, which is expensive to acquire and limited by the available resources of expert image analysts. Therefore, unsupervised, weakly-supervised and self-supervised feature learning techniques receive a lot of attention, which aim to utilise the vast amount of available data, while at the same time avoid or substantially reduce the effort of manual annotation. In this paper, we propose a novel way for training a cardiac MR image segmentation network, in which features are learnt in a self-supervised manner by predicting anatomical positions. The anatomical positions serve as a supervisory signal and do not require extra manual annotation. We demonstrate that this seemingly simple task provides a strong signal for feature learning and with self-supervised learning, we achieve a high segmentation accuracy that is better than or comparable to a U-net trained from scratch, especially at a small data setting. When only five annotated subjects are available, the proposed method improves the mean Dice metric from 0.811 to 0.852 for short-axis image segmentation, compared to the baseline U-net

Interobserver reliability of radial head fracture classification : two-dimensional compared with three-dimensional CT

Background: The Broberg and Morrey modification of the Mason classification of radial head fractures has substantial interobserver variation. This study used a large web-based collaborative of experienced orthopaedic surgeons to test the hypothesis that three-dimensional reconstructions of computed tomography (CT) scans improve the interobserver reliability of the classification of radial head fractures according to the Broberg and Morrey modification of the Mason classification.Methods: Eighty-five orthopaedic surgeons evaluated twelve radial head fractures. They were randomly assigned to review either radiographs and two-dimensional CT scans or radiographs and three-dimensional CT images to determine the fracture classification, fracture characteristics, and treatment recommendations. The kappa multirater measure (&kappa;) was calculated to estimate agreement between observers.Results: Three-dimensional CT had moderate agreement and two-dimensional CT had fair agreement among observers for the Broberg and Morrey modification of the Mason classification, a difference that was significant. Observers assessed seven fracture characteristics, including fracture line, comminution, articular surface involvement, articular step or gap of &ge;2 mm, central impaction, recognition of more than three fracture fragments, and fracture fragments too small to repair. There was a significant difference in kappa values between three-dimensional CT and two-dimensional CT for fracture fragments too small to repair, recognition of three fracture fragments, and central impaction. The difference between the other four fracture characteristics was not significant. Among treatment recommendations, there was fair agreement for both three-dimensional CT and two-dimensional CT.Conclusions: Although three-dimensional CT led to some small but significant decreases in interobserver variation, there is still considerable disagreement regarding classification and characterization of radial head fractures. Three-dimensional CT may be insufficient to optimize interobserver agreement.<br /

Caractérisation expérimentale en traction/compression/torsion d'un matériau biosourcé type PHA

National audienceDe nouveaux matériaux polymères biosourcés et biodégradables ont fait leur apparition depuis une dizaine d'années. Ces nouveaux matériaux sont une réponse intéressante aux problèmes de ressource et de recyclage-posés par les polymères classiques provenant de la pétrochimie. Ils présentent le double avantage d'être issus de la biomasse, mais également d'être compostables, c'est-à-dire qu'il ne génère aucun toxique en se dégradant, sous certaines conditions spécifiques d'humidité et de température. Nous nous intéressons dans ce travail à une classe particulière de ces nouveaux matériaux biopolymères produits par des micro-organismes : les PolyHydroxyAlkanoates (ou PHA). Les PHA sont des polymères biosourcés, produits par une grande variété de bactéries (Ralstonia, Pseudomonas,…) en tant que réserve énergétique intracellulaire. Ces matériaux présentent malgré tout un défaut important : leur élaboration reste encore souvent difficile à contrôler conduisant à un coût de production souvent prohibitif et limitant leur dissémination dans des secteurs plus conventionnels comme par exemple celui de l'emballage. Pour que ces matériaux aient une diffusion plus importante dans ce secteur, il s'avère nécessaire d'optimiser la forme et la tenue mécanique de ces produits d'emballage. Cela nécessite une bien meilleure connaissance de leur comportement mécanique encore peu connue pour l'instant. Dans ce contexte, cette étude a pour objectif de caractériser expérimentalement puis numériquement le comportement de nuances de PHA [1]. Le but est ensuite d'aboutir à un outil numérique de calcul, capable de dimensionner et simuler le comportement thermo-mécanique de pièces d'emballages en PHA telles que ceux produits par la société EUROPLASTIQUES, partenaire industriel de ce projet. Parallèlement à ce matériau biosourcé, nous étudions également un polymère plus classique, le polypropylène, avec deux objectifs. Tout d'abord l'idée est de valider la méthodologie d'essai, compte tenu du fait que l'on dispose déjà d'une identification partielle d'une nuance de polypropylène, le PPC7712 [2]. D'autre part, ce polypropylène étant également utilisé en emballage, il permettra des comparaisons finales sur les comportements de structures. Pour la caractérisation mécanique de ces matériaux, un dispositif original a été conçu permettant la réalisation d'essais de cycles multiaxiaux simultanés comprenant des phases de traction, torsion et de compression. Ce dispositif comprend une cellule de force à six axes et d'un montage spécifique pour le serrage et le maintien d'une éprouvette cylindrique (Figure 1). Cette éprouvette est obtenue par injection, elle se compose d'une partie cylindrique et de deux têtes hexagonales (Figure 2). Contrairement, aux essais classiques, où les éprouvettes sont maintenues et entraînées par serrage, l'éprouvette est ici liée par obstacle dans les deux sens des trois directions, sans serrage afin d'éviter, autant que possible, l'apparition de contraintes mécaniques initiales. Un système de mors comprenant des plateaux, des vis et des empreintes hexagonales permettent le blocage total de l'éprouvette, quel que soit l'essai envisagé. Le dispositif prend aussi en compte la dispersion prévisible des dimensions des têtes d'éprouvette par l'intermédiaire de lamelles flexibles entre l'accouplement au vérin et le blocage des têtes. Les déformations sont mesurées directement sur l'échantillon grâce à un dispositif de corrélation d'images en 3D (Aramis 4M, GOM), permettant également de vérifier l'homogénéité de la cinématique. Figure 2: Éprouvette de chargement multiaxial Figure 1: Dispositif d'essais multiaxiaux Ce montage original autorise des cycles de sollicitations successives ou combinées de traction, compression et de torsion (Figure 3), à partir d'une seule géométrie d'éprouvette. Dans la littérature, les essais de traction et de cisaillement sont réalisés habituellement avec des éprouvettes de géométrie spécifique à chaque essai. Dans ce cas, il est difficile d'être sûr d'étudier la même structure de matériau, celle-ci étant fortement dépendante du type d'élaboration et des cinétiques de refroidissement, elles-mêmes directement liées aux dimensions géométriques. Le dispositif expérimental développé ici permet d'effectuer des chemins complexes avec changements de direction et de cycles au cours d'un même essai et sur la même éprouvette, autorisant ainsi l'exploration de tout le plan déviatoire de déformation avec prise en compte de l'histoire du chargement. Pour la simulation du comportement de structures, nous utilisons un modèle de comportement 3D d'Hyper-Visco-Hystérésis (HVH) [2], implanté dans le code de calcul Herezh++ [3]. Il tient sa singularité au fait que le comportement du matériau est décomposé en une contribution additive. Tout en incluant un potentiel hyperélastique, cette loi permet de décrire le phénomène d'hystérésis non-visqueux ainsi qu'une dépendance au temps du matériau. Le protocole d'identification, permettant l'obtention des paramètres utiles à ce modèle, est simple et rapide car il ne nécessite qu'un unique type d'essais de traction/compression relaxation [4]

Microstructure Evolution in AM Produced Superalloy Thin Struts at Low Plastic Strain

This paper discusses the microstructures and textures that develop in thin struts fabricated in Inconel 718 using laser melting powder bed fusion. Thin struts 1 mm wide were fabricated in the vertical (ZX) and horizontal build (XY) orientations with respect to the build plate. Three distinct regions of well-defined grain structures with centerline symmetry from the outer border to the center of the inner volume were present, which was attributed to the laser scan strategy, consisting of a fill hatch, inner and outer border scan on each 30 m layer. Using ex situ micro-tensile testing and enhanced Back-Scattered Electrons (BSE) and Electron Back Scattered Diffraction (EBSD), the microstructure evolution to a plastic strain near 1%, in both the ZX and XY build direction was studied in the initial undeformed and final deformed states. For the ZX build direction, grain rotation as well as grain boundary migration was observed and was more significant than in the samples fabricated in XY. This paper discusses the evolution of the microstructure offering valuable insights into the relationship between microstructure and mechanical properties in complex AM produced microstructures

Adenylate effects on protein phosphorylation in the interenvelope lumen of pea chloroplasts

A 64-kilodalton (kDa) protein, situated in the lumen between the inner and outer envelopes of pea (Pisum sativum L.) chloroplasts (Soll and Bennett 1988, Eur. J. Biochem., 175, 301–307) is shown to undergo reversible phosphorylation in isolated mixed envelope vesicles. It is the most conspicuously labelled protein after incubation of envelopes with 33 nmol·1-1 [-32P]ATP whereas incubation with 50 mol·1-1 [-32P]ATP labels most prominently two outer envelope proteins (86 and 23 kDa). Half-maximum velocity for phosphorylation of the 64-kDa protein occurs with 200 nmol·1-1 ATP, and around 40 mol·1-1 ATP for phosphorylation of the 86- and 23-kDa proteins, indicating the operation of two distinct kinases. GGuanosine-, uridine-, cytidine 5-triphosphate and AMP are poor inhibitors of the labelling of the 64-kDa protein with [-32P]ATP. On the other hand, ADP has a potent influence on the extent of labelling (half-maximal inhibition at 1–5 mol·1-1). The ADP-dependent appearance of 32P in ATP indicates that ADP acts by reversal of kinase activity and not as a competitive inhibitor. However, the most rapid loss of 32P from pre-labelled 64-kDa protein occurs when envelope vesicles are incubated with ATP t1/2=15 s at 20 molsd1-1 ATP). This induced turnover of phosphate appears to be responsible for the rapid phosphoryl turnover seen in situ

Emerging pharmacotherapy of tinnitus

Tinnitus, the perception of sound in the absence of an auditory stimulus, is perceived by about 1 in 10 adults, and for at least 1 in 100, tinnitus severely affects their quality of life. Because tinnitus is frequently associated with irritability, agitation, stress, insomnia, anxiety and depression, the social and economic burdens of tinnitus can be enormous. No curative treatments are available. However, tinnitus symptoms can be alleviated to some extent. The most widespread management therapies consist of auditory stimulation and cognitive behavioral treatment, aiming at improving habituation and coping strategies. Available clinical trials vary in methodological rigor and have been performed for a considerable number of different drugs. None of the investigated drugs have demonstrated providing replicable long-term reduction of tinnitus impact in the majority of patients in excess of placebo effects. Accordingly, there are no FDA or European Medicines Agency approved drugs for the treatment of tinnitus. However, in spite of the lack of evidence, a large variety of different compounds are prescribed off-label. Therefore, more effective pharmacotherapies for this huge and still growing market are desperately needed and even a drug that produces only a small but significant effect would have an enormous therapeutic impact. This review describes current and emerging pharmacotherapies with current difficulties and limitations. In addition, it provides an estimate of the tinnitus market. Finally, it describes recent advances in the tinnitus field which may help overcome obstacles faced in the pharmacological treatment of tinnitus. These include incomplete knowledge of tinnitus pathophysiology, lack of well-established animal models, heterogeneity of different forms of tinnitus, difficulties in tinnitus assessment and outcome measurement and variability in clinical trial methodology. © 2009 Informa UK Ltd.Fil: Langguth, Berthold. Universitat Regensburg; AlemaniaFil: Salvi, Richard. State University of New York; Estados UnidosFil: Elgoyhen, Ana Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentin

Variation in Treatment for Trapeziometacarpal Arthrosis

Background: Treatment recommendations for trapeziometacarpal (TMC) arthrosis are highly variable from surgeon to surgeon. This study addressed the influence of viewing radiographs on a decision to offer surgery for TMC arthrosis. Methods: In an online survey, 92 hand surgeons viewed clinical scenarios and were asked if they would offer surgery to 30 patients with TMC arthrosis. Forty-two observers were randomly assigned to review clinical information alone and 50 to review clinical information as well as radiographs. The degree of limitation of daily activities, time since diagnosis, prior treatment, pain with grind, crepitation with grind, and metacarpal adduction with metacarpophalangeal hyperextension were randomized for each patient scenario to determine the influence of these factors on offers of surgery. A cross-classified binary logistic multilevel regression analysis identified factors associated with surgeon offer of surgery. Results: Surgeons were more likely to offer surgery when they viewed radiographs (42% vs. 32%, P = 0.01). Other factors associated variation in offer of surgery included greater limitation of daily activities, symptoms for a year, prior splint or injection, deformity of the metacarpophalangeal joint. Factors not associated included limb dominance, prominence of the TMC joint, crepitation with the grind test, and pinch and grip strength. Conclusion: Surgeons that view radiographs are more likely to offer surgery to people with TMC arthrosis. Surgeons are also more likely to offer surgery when people do not adapt with time and nonoperative treatment. Given the notable influence of surgeon bias, and the potential for surgeon and patient impatience with the adaptation process, methods for increasing patient participation in the decision-making process merit additional attention and study