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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1021

Host-Parasitoid Interactions of Two Invasive Drosophilids in Virginia Fruit Crops

Wahls, James Charles Edgar 18 May 2017 (has links)
1.) Sentinel traps were used to survey for parasitoids of frugivorous drosophilids in Virginia fruit cropping systems, and determine if parasitoids were attacking invasive flies Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) in the field. Two parasitoids of frugivorous drosophilids, Leptopilina boulardi (Barbotin, Carton, and Kelner-Pillault) (Hymenoptera: Figitidae) and Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae), were reared, but only one P. vindemiae was reared from D. suzukii, and no parasitoids were reared from Z. indianus. Most parasitoids were reared from alternate host Drosophila melanogaster Meigen and other wild drosophilids. 2.) The ability of these parasitoids to attack D. melanogaster, D. suzukii and Z. indianus under controlled conditions was tested. Larval parasitoid L. boulardi did not develop on D. suzukii or Z. indianus, just D. melanogaster. Pupal parasitoid P. vindemiae successfully developed on all three fly species, but also increased pupal fly mortality. 3.) Olfactometry was used to ascertain if L. boulardi and P. vindemiae are selective about the type of fruit their hosts feed in. Results showed that among cherry, raspberry, blueberry, grape, and banana, L. boulardi preferred raspberry and banana to cherry, and preferred grape least, but no fruit was most preferred. Insufficient data were obtained for P. vindemiae. We conclude that parasitoids of Virginia are unlikely to provide effective biological control for D. suzukii or Z. indianus, and classical biological control should be investigated as a pest management option. Olfactometry results indicate tritrophic selectivity by Drosophila parasitoids, suggesting multiple parasitoids could be required for effective biological control. / Master of Science in Life Sciences / The spotted wing drosophila (henceforth SWD) is a globally invasive vinegar fly originating from southeast Asia, and is economically damaging to producers of small fruit, such as berries, cherries, and grapes. The African fig fly (henceforth AFF), a relative of SWD, is another recently invasive species to North America (originating from Africa) that often occurs simultaneously with SWD infestations, but its economic threat to North America is still unclear. With the economic threat posed by SWD, and potential threat posed by AFF, it is important to understand their relationships with other organisms in their environment, especially natural enemies, such as parasitoid wasps. Such information is integral for researchers to develop effective control methods, and will help determine if natural enemies can be used to our advantage as biological control agents. Biological control also helps to limit the use of chemical insecticides, mitigating the development of insecticide resistance in the pests. This project employed unique field trapping methods and laboratory bioassays to investigate the relationships of SWD and AFF with parasitoid wasps in affected fruit cropping systems in southwestern Virginia. We discovered that parasitoids of vinegar flies are present in Virginia fruit cropping systems, but they do not help to control populations of SWD and AFF. The parasitoids that are present prefer to attack other fly species, are unable to attack SWD and AFF, or do not attack in high enough numbers to have an impact on SWD or AFF populations. Biological control success is more likely to come from parasitoid species that have co-evolved with SWD and AFF in their native ranges.
1022

Identification of Stage-Specific Breast Markers using Quantitative Proteomics

Shaheed, Sadr-ul, Rustogi, Nitin, Scally, Andy J., Wilson, J., Thygesen, H., Loizidou, M.A., Hadjisavvas, A., Hanby, A., Speirs, V., Loadman, Paul, Linforth, R., Kyriacou, K., Sutton, Chris W. 09 October 2013 (has links)
Yes / Matched healthy and diseased tissues from breast cancer patients were analyzed by quantitative proteomics. By comparing proteomic profiles of fibroadenoma (benign tumors, three patients), DCIS (noninvasive cancer, three patients), and invasive ductal carcinoma (four patients), we identified protein alterations that correlated with breast cancer progression. Three 8-plex iTRAQ experiments generated an average of 826 protein identifications, of which 402 were common. After excluding those originating from blood, 59 proteins were significantly changed in tumor compared with normal tissues, with the majority associated with invasive carcinomas. Bioinformatics analysis identified relationships between proteins in this subset including roles in redox regulation, lipid transport, protein folding, and proteasomal degradation, with a substantial number increased in expression due to Myc oncogene activation. Three target proteins, cofilin-1 and p23 (increased in invasive carcinoma) and membrane copper amine oxidase 3 (decreased in invasive carcinoma), were subjected to further validation. All three were observed in phenotype-specific breast cancer cell lines, normal (nontransformed) breast cell lines, and primary breast epithelial cells by Western blotting, but only cofilin-1 and p23 were detected by multiple reaction monitoring mass spectrometry analysis. All three proteins were detected by both analytical approaches in matched tissue biopsies emulating the response observed with proteomics analysis. Tissue microarray analysis (361 patients) indicated cofilin-1 staining positively correlating with tumor grade and p23 staining with ER positive status; both therefore merit further investigation as potential biomarkers. / Cyprus Research Promotion Foundation, Yorkshire Cancer Research
1023

Patienters erfarenheter av non-invasiv ventilation vidakut respiratorisk svikt : En integrativ litteraturstudie / Patients’ experiences of non-invasive ventilation in acute respiratory failure : An integrative literature review

Bonnarp, Theresia, Wargéus, Maria January 2024 (has links)
Bakgrund: Akut respiratorisk svikt är en vanlig sökorsak på akutmottagningar. Studier har visatatt NIV kan minska behovet av intubation och öka chansen för överlevnad hos patienter medsvåra andningsbesvär. Då specialistsjuksköterskan arbetar personcentrerat kan patientensupplevelse höras och därmed kan utfallet av NIV förbättras genom förståelse för patienterserfarenheter. Syfte: Syftet var att beskriva patienters erfarenheter av non-invasiv ventilation vid akutrespiratorisk svikt. Metod: Integrativ litteraturstudie med systematisk litteratursökning i databaserna PubMed,Cinahl och PsychInfo. Resultat: Resultatet baseras på 14 artiklar och är indelat i tre huvudkategorier: Behandlingenspåverkan, Vårdpersonalens påverkan och Psykosocial påverkan. Nio underkategorierpresenteras: Att bli hjälpt av behandlingen, Att uppleva besvär av behandlingen, Att känna stödfrån vårdpersonal, Att vara utlämnad, Att ha behov av information, Att utveckla strategier, Att haett behov av kontroll samt Att bli påverkad av personliga relationer. Slutsats: Patienters erfarenheter av NIV vid akut respiratorisk svikt varierade och både positivaoch negativa upplevelser beskrevs. Att genomgå behandling med NIV försätter patienten i ensårbar situation och om akutsjuksköterskan implementerar principerna för personcentreradomvårdnad kan patienters behov mötas vilket kan förbättra utfallet av behandlingen. / Background: Acute respiratory failure is a common reason for seeking emergency services.Studies have shown that NIV can reduce the need for intubation and increase the chance ofsurvival in patients with severe respiratory distress. As the specialist nurse works person-centred,the patient's experience can be heard and thus the outcome of NIV can be improved throughunderstanding the patients' experiences. Aim: The aim was to describe patients’ experiences of non-invasive ventilation in acuterespiratory failure. Method: Integrative literature study with systematic literature search in the databases PubMed,Cinahl and PsychInfo. Result: The result is based on 14 articles and is divided into three main categories: Impact of thetreatment, Impact of the healthcare staff and Psychosocial impact. Nine subcategories arepresented: Being helped by the treatment, Experiencing discomfort from the treatment, Feelingsupported by healthcare personnel, Being left out, Having a need for information, Developingstrategies, Having a need for control and Being affected by personal relationships. Conclusion: Patients' experiences of NIV in acute respiratory failure varied and both positiveand negative experiences were described. Undergoing treatment with NIV puts the patient in avulnerable situation and if the emergency nurse implements the principles of person-centerednursing, patients' needs can be met, which can improve the outcome of the treatment.
1024

From 'useful and interesting' to 'evil invaders': evolving perceptions of non-native species in the United States

Richards, Jeannine Hyde January 2002 (has links)
Boston University. University Professors Program Senior theses. / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / 2999-01-02
1025

Changes in benthic productivity and community composition following silver carp die offs: a mesocosm approach

Bowman, Jacob 01 December 2024 (has links) (PDF)
Invasive species are often both ecologically and economically detrimental, particularly in freshwater ecosystems where direct and indirect impacts of invasion interact with pre-existing anthropogenic stressors to magnify consequences for native communities and habitats. Planktivorous silver carp (Hypophthalmichthys molitrix) are invasive in the Mississippi River watershed, where their daily consumption of detrital seston can total more than half their body mass, and where they outnumber all native species combined in some river reaches. Because of these astonishing abilities, silver carp can cause basal resource changes, altering the body sizes and abundances of native plankton communities upon invasion. Much research has focused on this outcome of silver carp proliferation, but investigation into other effects of their presence in invaded systems has not received the same attention. Despite the unique tendency of silver carp to experience species-specific mass-mortality events, for example, there is a dearth of peer-reviewed evaluation of the possible ecological consequences of these occurrences. To elucidate the effects of these events which can comprise hundreds of thousands of individuals, we determined how the decomposition of silver carp carcasses following mass-mortality events affected benthic invertebrate community composition and productivity using a mesocosm approach. Each mesocosm was subjected to either the presence or absence of a silver carp carcass over the length of an eight-week experiment. Carcass presence created anoxic conditions in the mesocosms and acutely increased benthic invertebrate biomass and benthic periphyton growth. While acute, changes to benthic conditions following silver carp mass-mortality events are likely to have long-term effects in both invaded freshwater systems and their surrounding terrestrial landscapes. Given the magnitude of die-offs, it is possible that these events could cause ecosystem-level alterations. Further research, therefore, is needed into the additional impacts that may follow carcass decomposition to quantify and predict outcomes associated with continued silver carp invasion.
1026

Effects of Urban Borders on Synanthropic Mesopredator Movement and Risk of Toxoplasma Gondii Infection in the Protected Lands of Key Largo, Florida USA

Crandall, Kelly A 01 August 2024 (has links) (PDF)
Protected lands are an important source of food, shelter, and reproductive opportunities for wildlife, especially in urbanizing landscapes. When urban development abuts the edges of protected lands, synanthropic species can alter their foraging behaviors and movement to utilize human-supplemented resources throughout the urban-wild interface. Therefore, urban edges on protected lands can have pronounced effects on animal movement and ecosystem function. There is also increased risk of disease transmission where high densities of wild animals exist, or where domestic animals and wild species are interacting. In particular, members of the family Felidae, including domestic cats (Felis catus), can transmit the pathogenic parasite, Toxoplasma gondii (henceforth T. gondii) through their feces. Capable of infecting any warm-blooded host species, infection with T. gondii has been proven to cause increased risk-taking behaviors, stillbirths and congenital birth defects, and mortality in humans and a variety of wildlife species. Northern raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana) are urban adaptive species who often benefit from human-supplemented food sources such as unsecured garbage, and outdoor pet food, and may be exposed to T. gondii more frequently if they are utilizing resources close to cats. To investigate how urban edges of protected lands affect the movement and infection risk for urban-adapted mesopredators, I captured and attached GPS collars to opossums and raccoons between April 2022 and October 2023 in northern Key Largo, FL, USA, a protected area with large contiguous patches of undisturbed land cover adjacent to two distinct urban areas with high outdoor cat densities and available human-supplemented food resources. Using GPS collar data, I estimated home ranges and third-order resource selection of 27 raccoons and 12 opossums from Key Largo, FL. The average home range of opossums were 20.51 ha (14.12 SE) which was significantly smaller than raccoons (137.01 ha, 10.74 SE, t37 = -2.70, p = 0.01). The proportion of urban development in an individual’s home range was the most influential factor associated with home range size, followed by species and sex. Individuals with greater proportions of residential neighborhoods and commercial areas in their home ranges were associated with smaller home ranges. Third-order resource selection functions identified both mesopredator species using residential and commercial land use areas significantly more than they were available on the landscape. To survey for T. gondii infections, I collected blood samples from all the captured raccoons and performed a direct modified agglutination test (MAT) to detect antibodies for T. gondii. To understand how human-supplemented foods could be affected exposure rates, I collected hair samples from all raccoons and analyzed the stable carbon isotope ratios, so that higher ratios of carbon were equated to greater intake of non-natural, human-supplemented food resources. 67.7% (21/31; 95% CI: 51.3–84.2%) of the raccoons tested positive for T. gondii antibodies, and the proportion of urban development in an individual’s home range was the best predictor for infection. A multinomial regression analysis indicated that raccoons with higher levels of antibodies were also likely to have a majority “non-wild” diet based on δ13C values from a stable carbon isotope analysis. These results suggest the primary route of parasite transmission is contact with domestic cats, which may be exacerbated by the exploitation of human-supplemented food in urban areas. The Florida Keys are currently facing mammal population declines tied to Burmese pythons (Python bivitattus) and outdoor cat predations, and management policies that decrease the circulation of T. gondii oocysts in the environment are important to bolstering the fitness of these island-dwelling populations. Decreased reproductive success or behavioral changes that increase risk of predation could spell catastrophic for these mesopredator populations that are following in the footsteps of their Everglades counterparts, and at risk of extirpation on Key Largo. I recorded a systemic reduction of home range sizes on the urban edges of the protected areas of Key Largo, which often corresponds with higher densities of animals, which may increase probability of disease transmission, especially when the urban borders support populations of feral domestic species. As urbanization increases and the distance between wild lands and human disturbance decreases, it is increasingly important to study the mechanisms of how urban development on the edges of protected areas affect the ecology of wildlife species.
1027

RECRUITMENT SOURCES OF GRASS CARP (CTENOPHARYNGODON IDELLA) IN THE GREAT LAKES

Etter, Nicholas Steven 01 December 2024 (has links) (PDF)
Grass Carp (Ctenopharyngodon idella) is a species of concern in areas they have invaded, such the Laurentian Great Lakes, due to their potential to substantially reduce aquatic macrophyte coverage. Efforts to control Grass Carp in the Great Lakes have primarily been focused on two tributaries to the western basin of Lake Erie (i.e., Sandusky and Maumee rivers, Ohio) where reproduction has been documented, although other Great Lakes tributaries are known to have thermal and hydrological regimes suitable for Grass Carp spawning. Knowledge of sources contributing to the expanding population of invasive Grass Carp in the Great Lakes is key to allocating control efforts aimed at curbing further introductions, reducing natural recruitment, and limiting potential for further range expansion. A recent study demonstrated that otolith microchemistry is an effective tool for identifying the natal environment of Grass Carp in the Great Lakes. Increased captures of Grass Carp in Lake Erie and Lake Michigan indicates an ongoing need to determine which tributaries are supporting Grass Carp recruitment. Therefore, the objectives of this study were to use otolith stable oxygen isotope (δ18O) analysis to determine whether diploid and unknown ploidy Grass Carp collected from the Great Lakes during 2019-2022 were wild or of aquaculture origin, analyze Sr:Ca and Ba:Ca ratios of water samples collected from known and potential Grass Carp spawning tributaries to assess persistence of differences in water chemistry among tributaries observed in prior studies, use otolith core trace element ratios (Sr:Ca and Br:Ca) to infer natal rivers of wild Grass Carp, and estimate how many groups of aquaculture-origin Grass Carp (both diploid and triploid individuals) with distinct otolith chemistry profiles were present among fish collected during 2019-2022. Water Sr:Ca and Ba:Ca for Great Lakes tributaries were consistent with data from prior studies. Diploid and unknown ploidy Grass Carp (21%) were identified as aquaculture origin fish based on otolith core δ18O. Multiple clusters and broad ranges of otolith core Sr:Ca and Ba:Ca among aquaculture-source Grass Carp suggest multiple sources of introduced/escaped fish in the Lake Erie basin. Tributaries to the western basin of Lake Erie were identified as the primary sources of wild Grass Carp, although there was some evidence of recruitment from central or eastern basin tributaries to Lake Erie. There was no evidence of Grass Carp reproduction in the Lake Michigan basin; the one wild fish caught in the Lake Michigan basin had otolith core Sr:Ca consistent with origin in a western basin tributary of Lake Erie. Thus, efforts to control natural recruitment of Grass Carp should remain focused on tributaries to the western basin of Lake Erie, especially where reproduction has been documented. However, the relatively high percentage of aquaculture-source Grass Carp (including some fertile, diploid fish) captured during multi-agency response efforts indicates that curtailing natural recruitment, further introductions, and spread of Grass Carp is necessary for successful population control.
1028

Nitinol stabilization device for beating-heart procedures

Matthews, Grace A. 28 January 2025 (has links)
2025 / The current tools used in transcatheter procedures for interventional cardiology are often limited to one or two degrees of freedom as well as in their distal control, dexterity, and force output. These shortcomings greatly restrict which procedures can be translated from open-heart to transcatheter methods. To address these shortcomings, Rogatinsky et al. of the Morphable Biorobotics Laboratory (MBL) developed an interventional robot comprising a soft stacked balloon actuator (SBA) manipulator and a pop-up stabilization mechanism. The stabilization plays a critical role for the robot by moving the device fulcrum closer to the procedure site as well as creates a fixed reference point for the soft manipulator. The stabilization allows for greater mechanical leverage, force transmission, and predictable, controllable movement. This thesis draws inspiration from the stabilization mechanism from Rogatinsky et al. and presents a new stabilization design that can be successfully deployed in in vivo tests. This new design bears a segmented backbone, new pop-up geometry, different material, and an intuitive actuation system. This overall design allows the robot to navigate vasculature curves, make it robust against the unpredictability of the in vivo setting, increase the device’s mechanical and deployment failure threshold, and limit user error, respectively while matching and outperforming the initial design in respect to axial and radial perturbation resistance, and absence of vessel occlusion. These results allow the overall prototype to complete in vivo tests, a necessary step for product development toward clinical viability. / 2027-01-28T00:00:00Z
1029

Essays on Dynamic Optimization for Forest Resource Management

Chong, Fayu 28 February 2025 (has links)
The dissertation consists of three essays in forestry resource management, with focuses on investigating the ecosystem collapse and invasive species control problems. The first two papers consider the shift from primary forests to cleared land and secondary forests in the context of deforestation. This process is known to lead to irreversible tipping points that lead to the loss of ecosystem services. The past literature has discussed forest rotations under stochastic prices, timber volume, and amenity values. I extend this body of work to show how stochastic processes concerning primary forests could lead to ecological collapse. Drift and volatility in these processes explain different types of long-term and short-term shocks in tropical forest systems, such as fire, drought, or climate changes, all mechanisms that can drive ecosystem function to collapse. Common examples of severe ecosystem damage include the irreversible change from tropical forests to grassy savanna, fire events, and other climate problems. However, another case of uncertainty happens when ecosystem service production of primary and secondary forests itself is stochastic, so that there is a more complicated relationship between deforestation and reaching a point where ecosystem functions collapse. I compare and contrast these two cases to determine how drift and volatility determines the timing of a tipping point in a deforestation model where primary and secondary forests, as well as agricultural land, influence ecosystem function. I examine the sensitivity of the timing of collapse in both model variants to critical market and land-use parameters. The third chapter of this dissertation explores the connection between landowners' risk preferences, invasive species spread, and optimal control efforts. This study analyzes the control effort involved in neighboring infested and uninfested municipalities, which may have differing risk preferences. In the context of an application to the spread of Emerald ash borer (EAB) in the Twin Cities, Minnesota, I develop a simulation to explore the level of control and spread in a myopic policy scenario versus that in a first-best problem, where the two municipalities may be either risk neutral or risk averse. The results suggest that heterogeneity in risk aversion across the municipalities leads to lower control efforts and a longer time to drive the probability of spread to zero. / Doctor of Philosophy / This dissertation presents three studies that aim to support policy making for sustainable forest resource management. In the first two chapters, I examine the deforestation of native tropical forests, which damages ecosystems and leads to losses that can be irreversible, even with investments in reforestation. At present, the Amazon, Indonesia, and Africa are all witnessing the catastrophic collapse of forest systems as a result of deforestation. Prior work by economists on this topic has not considered how uncertainty in native forest losses may affect the likelihood of ecosystem collapse. Native forest losses may be uncertain when policymakers cannot fully control deforestation (as is often the case in developing countries) or when complex ecosystems are not well understood. I develop a model that incorporates long-term and short-term shocks in forest systems, such as fire, drought, or climate changes, all mechanisms that can drive the primary forest stock function to ecosystem collapse. Using this model, I examine the sensitivity of the timing of collapse to critical market and land-use parameters. In the final chapter of the dissertation, I present a novel model to study how risk preferences affect the management of invasive species. The model is inspired by the Emerald Ash Borer (EAB) infestation in the Twin Cities, Minnesota, which spread from St. Paul into Minneapolis and decimated valuable urban tree cover over the past several decades. I use the model to explore how differences in risk preferences between neighboring municipalities affect the control efforts they undertake, the probability of pest spread, and the consequent economic losses.
1030

Abdominal aortic aneurysm follow-up after endovascular repair in a canine model with non-invasive vascular elastography

Salloum, Elie 11 1900 (has links)
Le traitement chirurgical des anévrismes de l'aorte abdominale est de plus en plus remplacé par la réparation endovasculaire de l’anévrisme (« endovascular aneurysm repair », EVAR) en utilisant des endoprothèses (« stent-grafts », SGs). Cependant, l'efficacité de cette approche moins invasive est compromise par l'incidence de l'écoulement persistant dans l'anévrisme, appelé endofuites menant à une rupture d'anévrisme si elle n'est pas détectée. Par conséquent, une surveillance de longue durée par tomodensitométrie sur une base annuelle est nécessaire ce qui augmente le coût de la procédure EVAR, exposant le patient à un rayonnement ionisants et un agent de contraste néphrotoxique. Le mécanisme de rupture d'anévrisme secondaire à l'endofuite est lié à une pression du sac de l'anévrisme proche de la pression systémique. Il existe une relation entre la contraction ou l'expansion du sac et la pressurisation du sac. La pressurisation résiduelle de l'anévrisme aortique abdominale va induire une pulsation et une circulation sanguine à l'intérieur du sac empêchant ainsi la thrombose du sac et la guérison de l'anévrisme. L'élastographie vasculaire non-invasive (« non-invasive vascular elastography », NIVE) utilisant le « Lagrangian Speckle Model Estimator » (LSME) peut devenir une technique d'imagerie complémentaire pour le suivi des anévrismes après réparation endovasculaire. NIVE a la capacité de fournir des informations importantes sur l'organisation d'un thrombus dans le sac de l'anévrisme et sur la détection des endofuites. La caractérisation de l'organisation d'un thrombus n'a pas été possible dans une étude NIVE précédente. Une limitation de cette étude était l'absence d'examen tomodensitométrique comme étalon-or pour le diagnostic d'endofuites. Nous avons cherché à appliquer et optimiser la technique NIVE pour le suivi des anévrismes de l'aorte abdominale (AAA) après EVAR avec endoprothèse dans un modèle canin dans le but de détecter et caractériser les endofuites et l'organisation du thrombus. Des SGs ont été implantés dans un groupe de 18 chiens avec un anévrisme créé dans l'aorte abdominale. Des endofuites de type I ont été créés dans 4 anévrismes, de type II dans 13 anévrismes tandis qu’un anévrisme n’avait aucune endofuite. L'échographie Doppler (« Doppler ultrasound », DUS) et les examens NIVE ont été réalisés avant puis à 1 semaine, 1 mois, 3 mois et 6 mois après l’EVAR. Une angiographie, une tomodensitométrie et des coupes macroscopiques ont été réalisées au moment du sacrifice. Les valeurs de contrainte ont été calculées en utilisant l`algorithme LSME. Les régions d'endofuite, de thrombus frais (non organisé) et de thrombus solide (organisé) ont été identifiées et segmentées en comparant les résultats de la tomodensitométrie et de l’étude macroscopique. Les valeurs de contrainte dans les zones avec endofuite, thrombus frais et organisé ont été comparées. Les valeurs de contrainte étaient significativement différentes entre les zones d'endofuites, les zones de thrombus frais ou organisé et entre les zones de thrombus frais et organisé. Toutes les endofuites ont été clairement caractérisées par les examens d'élastographie. Aucune corrélation n'a été trouvée entre les valeurs de contrainte et le type d'endofuite, la pression de sac, la taille des endofuites et la taille de l'anévrisme. / Surgical treatment of abdominal aortic aneurysms is increasingly being replaced by EVAR using SGs. However, the efficacy of this less invasive approach is jeopardized by the incidence of persistent flow within the aneurysm, called endoleaks leading to aneurysm rupture if not properly detected. Hence, a life-long surveillance by computed tomography (CT) angiography on an annual basis is increasing the cost of EVAR, exposing the patient to ionizing radiation and nephrotoxic contrast agent. The mechanism of aneurysm rupture secondary to endoleak is related to a pressurization of the aneurysm sac close to the systemic pressure. There is a relation between sac shrinkage or expansion and sac pressurization. The residual pressurization of AAA will induce sac pulsatility and blood circulation in the sac thus preventing sac thrombosis and aneurysm healing. NIVE using the LSME may become a complementary follow-up imaging technique for EVAR. NIVE has the capability of providing important information on the thrombus organization within the aneurysm sac and on the detection of endoleaks. The characterization of the thrombus organization was not possible in a previous NIVE study. A limitation was the absence of CT examinations as gold standard for endoleak diagnosis. In the current study, we aimed to apply and optimize NIVE of AAA after EVAR with SG in a canine model to detect endoleaks and characterize thrombus organization. SGs were implanted in a group of 18 dogs with an aneurysm created in the abdominal aorta. Type I endoleak was created in 4 aneurysms, type II in 13 aneurysms and no endoleak in 1 aneurysm. DUS and NIVE examinations were performed at baseline, 1-week, 1-month, 3-month and 6-month follow-up after EVAR. Angiography, CT-scan and macroscopic tissue slides were performed at sacrifice. Strain values were computed using the LSME. Areas of endoleak, solid thrombus (organized) and fresh thrombus (non-organized) were identified and segmented by comparing the results of CT scan and macroscopic tissue slides. Strain values in areas with endoleak, organized and fresh thrombi were compared. Strain values were significantly different between endoleak and organized or fresh thrombus areas and between organized and fresh thrombus areas. All endoleaks were clearly characterized on elastography examinations. No correlation was found between strain values and type of endoleak, sac pressure, endoleak size and aneurysm size.

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