Simultaneous segmentation of the left and right heart ventricles in 3D cine MR images of small animals

New high resolution image techniques allow to capture the anatomy and movement of the heart of small animals. The availability of these in vivo images can be very useful for medical research, however the amount of generated data for large animal studies makes manual analysis a very tedious task. To cope with the problem of automatic analysis of these images, we propose the use of the Deformable Elastic Template method to perform automatic segmentation of the ventricles. To adapt the method to the specificities of high-resolution MRI, several improvements are presented, including an image-context dependent scheme for more robust segmentation. Qualitative results show that our method is able to correctly retrieve the heart’s contours in 3D. 1

Gluon distributions in nucleons and pions at a low resolution scale

In this paper we study the gluon distribution functions in nucleons and pions at a low resolution $Q^2$ scale. This is an important issue since parton densities at low $Q^2$ have always been taken as an external input which is adjusted through DGLAP evolution to fit the experimental data at higher scales. Here, in the framework of a model recently developed, it is shown that the hypothetical cloud of {\it neutral} pions surrounding nucleons and pions appears to be responsible for the characteristic valence-like gluon distributions needed at the inital low scale. As an additional result, we get the remarkable prediction that neutral and charged pions have different intrinsic sea flavor contents.Comment: final version to appear in Phys. Rev. D. Discussion on several points enlarge

Low Q2Q^2 wave-functions of pions and kaons and their parton distribution functions

We study the low $Q^2$ wave-functions of pions and kaons as an expansion in terms of hadron-like Fock state fluctuations. In this formalism, pion and kaon wave-functions are related one another. Consequently, the knowledge of the pion structure allows the determination of parton distributions in kaons. In addition, we show that the intrinsic (low $Q^2$) sea of pions and kaons are different due to their different valence quark structure. Finally, we analize the feasibility of a method to extract kaon's parton distribution functions within this approach and compare with available experimental data.Comment: 13 pages, 3 postscript figures include

Wolbachia in the Culex pipiens group mosquitoes: introgression and superinfection.

Wolbachia bacteria in mosquitoes induce cytoplasmic incompatibility (CI), where sperm from Wolbachia-infected males can produce inviable progeny. The wPip strain in the Culex pipiens group of mosquitoes produces a complexity of CI crossing types. Several factors are thought to be capable of influencing the expression of CI including Wolbachia strain type and host genotype. In this study, the unidirectional CI that occurs between 2 C. pipiens complex laboratory strains, Col and Mol, was further investigated by nuclear genotype introgression. The unidirectional CI between Col and Mol was not found to be influenced by host genetic background, in contrast to a previous introgression study carried out using bidirectionally incompatible C. pipiens group strains. A line containing both wPip strain variants superinfection was also generated by embryonic cytoplasmic transfer. The same crossing type as the parental Col strain was observed in the superinfected line. Quantitative polymerase chain reaction demonstrated a low density of the injected wPipMol variant in the superinfected line after 18 generations, which was considered likely to be responsible for the crossing patterns observed. The Wolbachia density was also shown to be lower in the parental Mol strain males compared with Col strain males, and no inverse relationship between WO phage and Wolbachia density could be detected

Development of a protocol for standardized use of a water-soluble contrast agent with polyethylene glycol in post-mortem CT angiography.

Computed tomography angiography (PMCTA) is increasingly used in postmortem cases. Standardized validated protocols permit to compare different PMCTA images and make it more easily to defend a case in court. In addition to the well-known technique by Grabherr et al. (2011) which is using paraffin oil as a carrier substance, water-soluble polyethylene glycol 200 (PEG200) can be used in combination with the contrast agent Accupaque® 300. As to date, there exists no standardized protocol for the use of this contrast agent mixture, the aim of this study was to develop a protocol using it. Between 2012 and 2022, 23 PMCTA with PEG200 and Accupaque®300 were performed at the University Centre of Legal Medicine Lausanne (Switzerland) and the Institute of Forensic Medicine Munich (Germany). The images obtained were evaluated regarding the opacification of the vessels and possible artefacts. The best image quality was obtained with a mixing ratio of 1:15 (Accupaque®300:PEG200) and a perfusion volume of 1000 ml in the arterial, 1400 ml in the venous and 350 ml in the dynamic phase. The infusion rates described by Grabherr et al. were confirmed for the three phases. Overall, the opacification of the vessels was diagnostically sufficient. In 13 cases no opacification of the right coronary artery was observed due to a stratification artefact. By using the PMCTA protocol with PEG200 as a carrier, a good overall image quality can be achieved. This protocol offers the possibility to standardize PMCTA with PEG200

Model computation and matching with the neuractive pyramid

This paper introduces the neuractive pyramids to model objects under elastic deformations . One pyramid is built on each frame of the image sequence . Each level of the pyramid is a regular graph that is recursively built on a low-pass version of the original picture . Cells of this graph deform to model the local information of the picture . Deformations are obtained by the minimization of an energy function computed both on the gradient of the picture and the graph structure . Each cell contains a vector of statistical moments computed on its domain and its neighborood . Matching pyramids defines a vector Field of local elastic transformations . The matching operator is based on a self-organizing map, introduced by Kohonen . Softness and multiresolution aspects of the pyramids allow accurate and robust results . An application to the matching of 2D cardiac MRI scans shows the interest of the method for deformable objects .Cet article présente les pyramides neuractives pour la modélisation des objets subissant des déformations élastiques. Une pyramide est construite pour chaque image de la séquence. Chaque niveau de la pyramide est un graphe régulier construit récursivement sur l'image de départ convoluée par un filtre passe-bas. Les cellules de ce graphe s'adaptent au contenu local des images. L'adaptation du graphe est obtenue en minimisant une fonction énergétique basée sur le gradient de l'image et la déformation des cellules. Chaque cellule reçoit un vecteur de moments statistiques calculé sur sa zone d'intérêt et celles de ses voisines. La mise en correspondance des pyramides permet d'accéder au champ de vecteurs des transformations élastiques locales. L'algorithme de mise en correspondance est fondé sur une approche neuronale auto-organisatrice. La souplesse et l'aspect multirésolution des structures permettent d'obtenir des résultats robustes et précis. L'application à des images cardiaques obtenues par résonance magnétique (IRM) 2D montre l'intérêt de la méthode pour la modélisation d'objets complexes

A dynamic 3-D cardiac surface model from MR images

Cardiac 3D + time segmentation and motion estimation are recognized as difficult prerequisite tasks for any quan-titative analysis of cardiac images. Some recent algorithms aim to consider a temporal constraint to increase the ac-curacy of results. To improve the temporal consistency, prior knowledge about cardiac dynamics can be used. In this paper, we propose to build a new Statistical Dynamic Model (SDM) of the heart by learning through a popula-tion of healthy individuals. This SDM is composed by a set of semi-landmarks which describe the heart surfaces. For each of them, a mean trajectory and variability around it are derived. The SDM provides a reasonable constraint for a temporally regularized segmentation and motion track-ing algorithm. 1

Clinical Characteristics of Suicidal Youths and Adults: A One-Year Retrospective Study

Suicide is a major mental health problem, particularly during youth, when it is the second leading cause of death. Since young people at risk of suicide are often cared for by the adult health system, we sought to identify the specificities and similarities between suicidal youths and adults in order to further inform the potential need for adaptations in taking care of suicidal youths. For this study, we used the following data: mental disorders, treatments, previous hospitalization, and reasons for current hospitalization, that were collected from November 2016 to October 2017 among people hospitalized for a suicidal crisis in a specialized psychiatric unit. First, we compared the data from the youth group with those from the adult group, and then we tried to determine if there were any associations between variables. Analyses showed that youths were more similar to adults than expected. In particular, we found comparable rates of personality disorders (especially borderline) and relapse, and similar profiles of reasons for hospitalization in suicidal crisis. Remarkably, among youth, neuroleptics appeared to be associated with fewer hospitalizations for behavioral than ideational reasons, but with more relapses. Results of this study suggest that young people could benefit from brief psychotherapeutic interventions implemented for adult

Optimal co-occurrence matrix for automatic segmentation of ultrasonic images

This paper introduces a new method of segmentation using automatic thresholding adapted to the NDT ultrasonic images . This study is based on image analysis through co-occurrence matrixes . It shows an optimization of the r and 0 parameters of the co-occurrence matrix enabling to define more acurately the border between noise and defect echoes . The segmentation is obtained by automatically taking into account a threshold derived from a determination curve calculated front the co-occurrence matrix . This curve, called Average Product of Variances Measure, is an analysis of the distribution of the matrix coefficients . The results show behaviors of the co-occurrence matrixes and of the threshold selection curves that justify perfectly the analysis performed on the characteristics of the image .Cet article présente une nouvelle méthode de segmentation par seuillage automatique, adaptée aux images obtenues en contrôle non destructif par ultrasons. Cette étude est fondée sur l'analyse d'image par matrice de co-occurrence. On présente une optimisation des paramètres r et Θ de la matrice de co-occurrence permettant de mieux définir la frontière qui sépare le bruit des échos de défauts. La segmentation s'obtient par la prise en compte automatique d'un seuil issu d'une courbe de détermination calculée à partir de la matrice de co-occurrenc

Asymptotic expansion for reversible A + B <-> C reaction-diffusion process

We study long-time properties of reversible reaction-diffusion systems of type A + B C by means of perturbation expansion in powers of 1/t (inverse of time). For the case of equal diffusion coefficients we present exact formulas for the asymptotic forms of reactant concentrations and a complete, recursive expression for an arbitrary term of the expansions. Taking an appropriate limit we show that by studying reversible reactions one can obtain "singular" solutions typical of irreversible reactions.Comment: 6 pages, no figures, to appear in PR