La validation des algorithmes de tractographie et l’optimisation des paramètres choisis en référence à une vérité terrain, sont primordiales avant l’utilisation de ces méthodes en routine clinique. D’une part, nous présentons une méthode de comparaison quantitative de reconstructions issues de la tractographie à celles reconstruites depuis la dissection par un scanner laser. Cette comparaison permet d’évaluer les reconstructions de différents modèles et algorithmes de tractographie (déterministe, probabiliste) en les confrontant à une vérité terrain acquise par le scanner laser (surfaces triangulées). La transformation des données sous des formats communs était nécessaire avant leur comparaison quantitative. Deux méthodes de comparaison, surface-surface et volume-volume ont été proposées. D’autre part, nous présentons une méthode d’optimisation par algorithme génétique (AG), des paramètres de tractographie déterministe. L’AG est un algorithme itératif d’optimisation basé sur la sélection naturelle, il est capable d’optimiser des problèmes complexes ayant plusieurs paramètres. Etant donné la vérité terrain d’un faisceau, l’AG se propose de trouver le jeu de paramètres optimal donnant le meilleur résultat de tractographie. Les méthodes de comparaisons et d’optimisation ont été appliquées à un faisceau d’objet test puis à deux faisceaux disséqués à partir d’un cerveau humain post mortem après acquisitions IRM et scanner laser. / Tractography validation and optimization of tracking parameters against a ground truth are mandatory before a large clinical use. First, we present a method to quantitatively compare tractography reconstructions to a ground truth derived from laser scanner acquisitions of dissected specimens. This comparison allows evaluation of multiple models and tractography approaches (deterministic, probabilistic…). The ground truth used for this comparison was acquired from dissected specimens using a surface laser scanner, which produces triangulated surface meshes. Data transformation to a common format was necessary before quantitative comparisons. Two comparison methods were proposed, surface-to-surface and volume-to-volume. Second, we propose a method for automatic optimization of deterministic tractography parameters using a genetic algorithm (GA). The GA is an iterative optimization algorithm based on natural selection, which is able to optimize complex problems having several parameters. For a given ground truth fasciculus, the GA was expected to find the set of tractography parameters producing the best tractography result according to the ground truth. The comparison and optimization methods were applied to a synthetic bundle derived from a phantom and to two dissected white matter tracts of a human post mortem brain.

Objectifs : caractériser (1) la morphométrie de la crosse afin d’examiner les critères favorisant les complications et la faisabilité d’endoprothèses (EP) standards. (2) les propriétés mécaniques de l’aorte ascendante (AA) chez le porc, homme sain et en cas de dissection aortique (DAo).Matériels et méthodes :Caractérisation morphométrique : A partir d’angioscanner aortiques les paramètres: (1) morphométriques élémentaires (2) géométriques ; (3) troncs supra-aortiques (TSAo), sont mesurésCaractérisation mécanique : In vivo : à partir de données échographiques et hémodynamiques, les paramètres élastiques sont calculés.In vitro : tests de traction bi-axiale sur l’AA plus une analyse histomorphométrique et microstructurale.Résultats :Caractérisation morphométrique : > de75% des patients ont une orientation des TSAo à ± 15° par rapport à la moyenne, et une variabilité de la distance entre les ostia TSAo de ± 4 mm.Les facteurs indépendants associés aux endofuites, défaut d’apposition et mal-positionnement sont respectivement:(1) collet proximal court; (2) angulation de la zone d’ancrage (valeur seuil 51°); et (3) indice tortuosité (valeur seuil 1.68) Caractérisation mécanique : In vivo : une grande compliance de l’aorte porcine comparé à l’homme et une rigidification en cas de DAo.In vitro : l’aorte porcine a un comportement linéaire comparé au caractère non linéaire chez l’homme. Conclusion : Ce travail montre :- le lien entre morphométrie et complications après EP, et la faisabilité d’EP standards pour la crosse.- le modèle porcin est inapproprié pour tester les EP de l’AA. - la rigidification de la paroi en cas de DAo influencera le choix des futurs EP. / Objectives: characterize (1) arch morphometry to examine criteria favoring complications after thoracic endovascular aortic repair (TEVAR) and feasibility of « off-the-shelf » fenestrated devices.(2) mechanical properties of ascending aorta (AA) in swine and humans, with and without aortic dissection.Materials and methods : Morphometric characterization : Computed tomographic angiography were analysed to calculate elementary morphometric, geometric and supra-aortic trunks data Mechanical characterization : In vivo: arterial pressure and diameters measured with echocardiophy are used to calculate elastic parameters.Ex vivo: biaxial tensile testing performed on AA plus histological and microstructural analysis. Results :Morphometric characterization : In > 75% of cases supra-aortic branches are positioned within 15° of each other and distances between them have a variability of ± 4 mm.Independant factors associated with endoleak, bird beak and mis-positioning are respectively : (1) short proximal neck (2) landing zone angulation (cut-off value: 51°); and (3) tortuosity index (cut-off value: 1.68). Mechanical characterization : in vivo: greater compliance of swine aorta compared to humans and a stiffer aorta in case of aortic dissectionBiaxial testing: linear stress-strain behavior of swine aorta, compared to a non linear one in human. Conclusion : our study reveals :- the impact of anatomy on complications occurrence after TEVAR, and suitable arguments for « off-the-shelf » fenestrated devices.- swine model is inappropriate to test AA dedicated stent-graft.- stiffer wall in aortic dissection has consequences on the choice of futur devices dedicated to AA.

Nous présentons dans cette étude nos travaux concernant le recalage 3D/2D d'images de dissection aortique. Son but est de de proposer une visualisation de données médicales, qui pourra servir dans le contexte de l'assistance peropératoire durant les procédures endovasculaires.Pour effectuer cette tâche, nous avons proposé un modèle paramétrique de l'aorte, appelé enveloppe tubulaire. Il sert à exprimer la forme globale et les déformations de l'aorte, à l'aide d'un nombre minimal de paramètres.L'enveloppe tubulaire est utilisée par les algorithmes de recalage proposés dans cette étude.Notre méthode originale consiste à proposer un recalage par calcul direct de la transformation entre image 2D, i.e. sans procéssus d'optimisation, et est appelée recalage par ITD .Les descripteurs, que nous avons définis pour le cas des images d'aorte, permettent de trouver rapidement un alignement grossier des données. Nous proposons également l'extension de notre approche pour la mise en correspondance des images 3Det 2D.La chaîne complète du recalage 3D/2D, que nous présentons dans ce document, est composée de la technique ITD et de méthodes précises iconiques et hybrides. L'intégration de notre algorithme basé sur les descripteurs en tant qu'étape d'initialisation réduit le temps de calcul nécessaire et augmente l'efficacité du recalage, par rapport aux approches classiques.Nous avons testé nos méthodes avec des images médicales, issues de patients trîtés par procédures endovasculaires. Les résultats ont été vérifiés par les spécialistes cliniques et ont été jugés satisfaisants; notre chaine de recalage pourrait ainsi être exploitée dans les salles d'interventions à l'avenir. / In this study, we present our works related to 3D/2D image registrationfor aorti dissition. Its aim is to propose a visualization of medial datawhih an be used by physians during endovas ular proedures.For this purpose, we have proposed a parametrimodel of aorta, alleda Tubular Envelope. It is used to express the global shape and deformationsof the aorta, by a minimal number of parameters. The tubular envelope isused in our image registration algorithms.The registration by ITD (Image Transformation Descriptors) is our ori-ginal method of image alignment : itomputes the rigid 2D transformation between data sets diretly, without any optimization process.We provide thedefinition of this method, as well as the proposition of several descriptors' formulae, in the base of images of aorta. The technique allows us to quickly and a poarse alignment between data. We also propose the extension of theoriginal approach for the registration of 3D and 2D images.The complete chain of 3D/2D image registration techniques, proposedin this document, consists of the ITD stage, followed by an intensity basedhybrid method. The use of our 3D/2D algorithm, based on the image trans-formation descriptors as an initialization phase, reduces the computing timeand improves the efficiency of the presented approach.We have tested our registration methods for the medical images of several patients after endovasular treatment. Results have been approved by our clinical specialists and our approach.We have tested our registration methods for the medical images of several patients after endovascular treatment. Results have been approved by our clinical specialists and our approach may appear in the intervention rooms in the futur.

No description available.

Aortic dissection is a detrimental disease with a high mortality. However, the mechanisms regulating the susceptibility to aortic dissection remain unknown. We hypothesize that endothelial oxidative stress due to the activation of the reactive oxygen species (ROS)-generating Nox2 enzyme may play an important role in the development of aortic dissection. To investigate this, we generated transgenic mice (C57BL/6J background) with endothelial specific over-expression of Nox2 (Nox2 Tg) under the control of a tie-2 promoter. Expression of the human Nox2 transgene was confirmed by qRT-PCR to be found only in endothelial cells (EC) isolated from transgenic mice, and not in Wt EC or vascular smooth muscle cells (VSMC) and macrophages isolated from either genotype. Wild-type (Wt) littermates and Nox2 Tg male mice (22-24 weeks old, n=11) were treated with saline or Ang II (1mg/kg/day) via subcutaneous mini-pump for 28 days. There was no significant difference in the pressor responses to Ang II between Wt and Nox2 Tg mice (Wt 121±7mmHg vs. Nox2-Tg 122±6mmHg). However, 5/11 Nox2 Tg mice developed aortic dissections compared to 0/11 Wt mice (P<0.05). Immunohistochemistry revealed significant increases in endothelial VCAM-1 expression, MMP activity and CD45+ inflammatory cell recruitment in the aortas of Nox2 Tg mice after 5 days of Ang II infusion. Inflammatory cell recruitment was confirmed by FACS analysis of cells from digested aortas (P<0.05). Explanted aortas from Nox2-Tg mice had significantly greater secreted pro-inflammatory cytokine, Cyclophilin A (CypA) both at baseline and after 5 days of Ang II infusion compared to Wt littermates. Compared to primary Wt EC and VSMC, Nox2-Tg primary EC, but not primary VSMC, had increased ROS production which was accompanied by increased endothelial CypA secretion and ERK1/2 activation. Furthermore, conditioned media from Nox2-Tg EC induced greater ERK1/2 phosphorylation compared to conditioned media from Wt controls. Knockdown of CypA from sEND.1 endothelial conditioned media by siRNA knockdown abolished VSMC Erk1/2 phosphorylation. In conclusion, we demonstrate for the first time that a specific increase in endothelial ROS through the over-expression of Nox2 was sufficient to induce aortic dissection in response to Ang II stimulation. Endothelial secreted CypA could be the signalling mechanism by which increased endothelial ROS regulates the inflammatory response and the susceptibility to aortic dissection.

Denote by gdist(p) the least number of cells that have to be changed to get a latin square from the table of addition modulo prime p. A conjecture of Drápal, Cavenagh and Wanless states that there exists c > 0 such that gdist(p) ≤ c log(p). In this work we prove the conjecture for c ≈ 7.21, and the proof is done by constructing a dissection of an equilateral triangle of side n into O(log(n)) equilateral triangles. We also show a proof of the lower bound c log(p) ≤ gdist(p) with improved constant c ≈ 2.73. At the end of the work we present computational data which suggest that gdist(p)/ log(p) ≈ 3.56 for large values of p.

Introdução. Leishmanioses são zoonoses que têm como agentes etiológicos tripanossomatídeos de várias espécies do gênero Leishmania. Elas são transmitidas aos hospedeiros vertebrados por Phlebotominae (Diptera, Psychodidae). As infecções por Leishmania podem se manifestar nas formas visceral (LV) e tegumentar (LT); ambas são sérios problemas de saúde pública no Brasil, que se encontra entre os países do mundo com as mais altas incidências. Dentre as atividades de controle das leishmanioses, as da vigilância entomológica estão voltadas para a redução da taxa de contato dos vetores com os hospedeiros vertebrados e identificar áreas de risco de transmissão. Neste sentido, a detecção de fêmeas de flebotomíneos naturalmente infectadas por Leishmania constitui-se numa das estratégias. Essa detecção pode ser realizada apenas por meio de análises moleculares ou estas serem precedidas de dissecção das fêmeas para observação da presença de flagelados em seus tratos digestórios. A observação dessas formas no trato digestório pode indicar a capacidade do parasita em resistir aos processos de sua eliminação, dependendo do local onde se encontra, e a que subgênero (Leishmania ou Viannia) pertence. No Brasil, a LV tem sido associada a espécie Leishmania (Leishmania) infantum. A LT tem como agentes espécies de ambos os subgêneros. O presente projeto teve como objetivo desenvolver um manual no qual são descritos os processos para se realizar a investigação da infecção natural por flagelados em fêmeas de flebotomíneos. Materiais e Métodos. Para a elaboração do manual foram examinadas fêmeas selvagens e outras provenientes de colônias alimentadas em hamsters infectados experimentalmente por Leishmania braziliensis e, posteriormente, dissecadas e examinadas em microscópio. Os parasitas utilizados nos experimentos de infecção em laboratório são oriundos de cultivos mantidos em laboratório. As espécies examinadas foram Lutzomyia longipalpis, Nyssomyia neivai e Pintomyia fischeri. Foram descritos os cuidados necessários à preservação dos espécimes em campo e transporte ao laboratório, de modo a tornar viável a dissecção e exame dos espécimes. As capturas realizadas em campo para o estudo permitiram tanto a obtenção dos espécimes como a elaboração do item que trata dos cuidados com as amostras. A documentação das múltiplas etapas de dissecção e exame dos espécimes necessários para o estudo foram realizados por meio de câmera fotográfica acoplada a microscópio óptico. Resultados. São apresentados na forma de manual. Neste são descritos e ilustrados aspectos das técnicas de captura, cuidados com os insetos no campo e laboratório, transporte de amostras vivas, o processo de dissecção da fêmea e a observação de seu tubo digestório para a investigação da presença de flagelados, e de estruturas de sua genitália, para a identificação da espécie de flebotomíneo. Apresenta-se ainda um protocolo a ser utilizado na preservação dos espécimes que forem encontrados infectados para posterior análise molecular e identificação específica do parasita. Conclusões. Com os tópicos apresentados no manual, espera-se contribuir com o programa vigilância epidemiológica das leishmanioses, em atividades da vigilância entomológica voltadas para a identificação de áreas de risco de transmissão dessas doenças e obter evidências que apontem para o potencial de espécies que possam estar atuando como vetores permissíveis de Leishmania spp. / Introduction. Leishmaniases are zoonoses having trypanosomatids of several species of the genus Leishmania as etiological agents, transmitted to vertebrate hosts by the bite of females of Phlebotominae (Diptera, Psychodidae). These parasitoses can manifest in visceral (VL) and tegumentary (TL) forms, both being serious public health problems in Brazil, which is among the countries of the world with the highest incidence rates. Among the activities of control of leishmaniases, those of entomological surveillance are aimed at reducing the contact rate of the vectors with the vertebrate hosts and also to identify areas in risk of the disease transmission. In this sense, the detection of sand fly females naturally infected with Leishmania is one of the strategies. This detection can be carried out exclusively by means of molecular analyzes or these being preceded by dissection of the females to observe the presence of flagellates in their guts. The observation of flagellate forms in the gut indicates the ability of the parasites to resist the processes of their elimination, and also to identify the subgenus (Leishmania or Viannia) to which the parasites belong. In Brazil, the VL infection is attributed to Leishmania (Leishmania) infantum, while in TL, there are various agents belonging to both subgenera. Objective. To develop a manual in which the processes for the investigation of the natural infection by flagellates in sand fly females are described and illustrated. Material and Method. For the construction of the manual, observation of infection by flagellates was made through the dissection of wild or laboratory females of Lutzomyia longipalpis, Nyssomyia neivai and Pintomyia fischeri, experimentally infected with Leishmania braziliensis. The description of care in the preservation of the specimens in the field and in their transport to the laboratory, in order to make feasible the dissection, was made based on the collection undertaken in this project. The documentation was made by means of a photographic camera coupled to an optical microscope. Result. A manual is presented describing and illustrating aspects of collection techniques, insect care in the field and laboratory, transport of the live samples, the dissection process and observation, respectively, of the female gut for the investigation of the flagellate presence and genitalia structure for the identification of the phlebotomine species. Protocol is also presented to be used in the preservation of the specimens found infected for subsequent molecular analysis and the specific identification of the parasite. Conclusions. With the topics presented in this manual, we intend to contribute to the program of epidemiological surveillance of leishmaniases, in activities of entomological surveillance, in the identification of areas of risk of transmission of these diseases, as well as to obtain evidence about the potential of species that may act as permissible vectors of Leishmania spp.

A normal aortic valve has three leaflets; however, 1- 2% of children are born with an aortic valve with two leaflets, referred to as congenital bicuspid aortic valves (BAV). Recent in vivo studies have shown that flow development past the bicuspid valves into the ascending aorta is markedly different from that past the normal tri-leaflet aortic valve. This difference may lead to the bicuspid valve having a higher rate of ascending aortic root dissection, a pathology that can potentially result in fatality. Using computational fluid dynamics we aim to evaluate the alterations in flow development in the ascending aorta with BAV compared to healthy tri-leaflet valves (TAV) and relate the alterations in flow-induced stresses with higher incidences of aortic dissection in patients with BAV. Simplified models based on the geometry and dimensions from published literature were developed. The preliminary results show that there is a difference in flow development between the BAV and the tri-leaflet valve. This is visible by the differences in wall shear stress and dynamic pressure distribution in the ascending aorta. The conclusion drawn from this is that there are marked differences in the ascending aortic flow development with BAV compared to that with TAV which may lead to dissection of the aortic arch.

Analyse der Landschaftszerschneidung und -fragmentierung, Untersuchung und Anwendung verschiedener Zerschneidungsgeometrien und deren Implementierung für unterschiedliche Indikatoren. Die Ergebnisse des methodischen Vergleiches für den Landkreis Havelland sollen die Grundlage für die Auswahl der geeignetesten Methode bei einer landesweite Untersuchung in Brandenburg liefern. / Analysis of landscape fragmentation and dissection using different dissection geometries and application to different indicators. The comparison of different methods for the Havelland county will be used as the base to choose the best method for a statewide analysis in Brandenburg.

Humans are extremely sensitive and accurate about detecting the amount of symmetry that a face possesses. However perception of facial symmetry has not been investigated in terms of its neural correlates yet. In this thesis, we investigated localization of facial symmetry perception in the brain through the use of the fMR-adaptation method. In this method, marginally active neuronal populations can be detected by presenting faces with varying symmetry. By standardizing all aspects of the faces such as illumination, pose and contrast, we manipulated only the amount of fluctuating asymmetry in the face images. Previous studies have shown that a specific area, lateral occipital complex (LOC) exhibits sensitivity to orientation and position changes to faces and other objects. We observed that facial symmetry activation is specifically localized within the LOC boundaries. Within the LOC, we found that previously defined areas namely LO1 and LO2 are both responsive to manipulations of facial symmetry. We also tested our fMR-adaptation paradigm on non-face images, generated by scrambling the face stimuli used in our experiments. We replicated earlier results which demonstrated that LO1 and LO2 are activated in detecting differences between symmetric versus asymmetric patches. This suggests that although facial symmetry perception is not processed by a function specific area of the LOC, it uses main resources allocated for the object recognition system in an efficient manner. To the best of our knowledge, our study is the first to investigate face symmetry perception through fMR-adaptation.