Effect of Channelized and Unchannelized Lateral Outflow on Three-Dimensional Flow Structure and Sediment Transport Mechanisms in a River Delta

Spatial and temporal patterns in three-dimensional flow structure have been linked to channel morphology and processes in many environments, including river meander bends, confluences-diffluences, and bedrock canyons. However, there is not yet an understanding of how channelized and gradual, distributed lateral outflows that are often prevalent in deltaic distributary systems influence three-dimensional flow structure and sediment transport mechanisms. This thesis presents an analysis of 3D flow structure data collected from Wax Lake Delta, a naturally developing river-dominated delta in the northern Gulf of Mexico. Three hydrographic surveys were conducted using boat-mounted acoustic Doppler current profiler (ADCP) at two sites: an asymmetrical bifurcation and a distributary channel experiencing distributed lateral outflow. Flow structure data from these surveys were investigated to identify secondary circulation cells induced by lateral outflow, which may influence the sediment transport to the islands. Spatial patterns in flow structure were also compared to previous numerical modeling and experimental studies on open channel diversions and compound channels to define the preconditions behind the formation of these secondary cells. The results are then used to develop a conceptual model linking the formation of secondary circulation cells and suspended sediment transport from the distributary channels to interdistributary islands in a delta. The results suggest the mechanisms of sediment transport into the islands from the channels may depend on a threshold momentum flux ratio per unit length of outflow value of which lies in between 0:211km-1 and 0:344km-1. This study provides the first detailed quantification of flow structure in an actively prograding river delta and offers important implications for coastal restoration by linking coastal sediment transport mechanism to patterns in flow structure

Three-Dimensional Flow, Morphologic Change, and Sediment Deposition and Distribution of Actively Evolving Neck Cutoffs Located on the White River, Arkansas

Neck cutoffs are important and prominent features of alluvial rivers yet detailed field-based research of neck cutoffs has been insufficient to fully characterize three-dimensional flow, morphologic change, and sediment deposition and distribution. The main objectives of this research are to examine the formation and evolution of neck cutoffs by characterizing the flow field, morphology, and sediment distribution through neck cutoffs with complex planform configurations located on the White River, Arkansas. Results led to the production of two conceptual models. The flow model has main hydrodynamic characteristics of (1) tight bend flow resulting from flow redirection of nearly 180° through the point of cutoff, (2) a zone of flow separation and recirculation adjacent to the cutoff junction corner within the downstream limb, (3) zones of recirculation at the entrance and exit of the abandoned loop, (4) highly asymmetric flow through the cutoff channel, (5) a zone of recirculation along the outer bank within the apex region of the downstream loop, and (6) reversal of helical flow. The morphologic model shows (1) the formation of a longitudinal bar in the upstream meander limb, (2) the development of a deep scour hole in the downstream meander limb, 3) erosion of the bank opposite the cutoff in the downstream meander limb, 4) a cutoff bar in the downstream meander limb at the junction corner of the cutoff channel and the downstream meander limb, and 5) perching of the exit of the abandoned bend above the cutoff channel due to channel bed incision. A combination of sediment cores, surface and grab samples, and dune tracking were used to estimate bedload sediment transport and sediment distribution through two of the neck cutoffs. Results indicate similar bedload sediment transport during bankfull and flood stages and revealed mixed load deposition associated with cutoffs that plug slowly is occurring within the abandoned bends. The research should result in invaluable information about hydrodynamic and morphologic processes of neck cutoffs, refine current conceptual models of neck cutoffs, and contribute to our understanding of meandering rivers with complex planform configurations

Bulle-Effect and its implications for morphodynamics of river diversions

Bifurcations are one of the fundamental elements of a fluvial (river) system, and diversions are a special type of asymmetrical bifurcation where one of the channels after bifurcation continues along the original channel. Diversions can be found in nature, though many of them are built to divert water and sediment from the river for various purposes. Historically, diversions were built to divert water for irrigational and navigational purposes. Recently the importance of diversions has increased, as building diversions to divert sediment (and water) have been put forth as a method to rebuild deltas that have been losing land due to rapid rise in sea-level, subsidence etc. One of the prime examples is the plan under consideration by United States Army Corps of Engineers (USACE) to re-build the Mississippi river delta through diverting water and sediment from the lower Mississippi river. Design of aforementioned diversions would be immensely benefited by a better understanding of the sediment distribution at diversions, and the hydrodynamics that drive it. One of the first and most extensive experimental studies to understand the dynamics at a diversion was conducted by Bulle in 1926, at Karlsruhe, Germany. Bulle found that a disproportionate percentage of bedload went into the lateral-channel, compared to the percentage of water entering the lateral-channel. This non-linear distribution of near-bed sediment between the two channels at a diversion is known as the Bulle-Effect; and since the seminal work of Bulle, multiple experimental studies have corroborated the phenomenon. Despite the importance of this phenomenon, till date the exact mechanism behind the Bulle-Effect is not clear. This thesis first unravels the mechanism behind the phenomenon, and then explores how Bulle-Effect might impact the morphodynamics of a diversion. This thesis can be divided into two major parts: 1) First the mechanism behind the Bulle-Effect phenomenon is explored using high-resolution numerical simulation (Direct Numerical Simulations, Large Eddy Simulations) of flow and sediment transport for a configuration and at the scale similar to Bulle’s experiment. The simulations were conducted using the highly-scalable spectral-element based incompressible Navier-Stokes solver Nek5000, on which a Lagrangian point particle submodel was developed and implemented to model the transport of sediment. The simulations were computationally very expensive (∼ 240 million computational points), thus they required the use of the peta-scale supercomputer Blue Waters for conducting them. The simulation results showed that the phenomenon is caused by the mechanism, where most of the flow near the bottom entered the lateral-channel, even when the percentage of the total water discharge entering lateral-channel is relatively smaller. The phenomenon was found to be at play not only for sediment transported as bed- load, but also for suspended sediment that travels in the lower 25-35 percent of the water-column. These findings were found to hold across a range of Reynolds number (10 − 25000) of the flow, and for different diversion angles. 2) In the second part of the thesis, a Reynolds Averaged Navier-Stokes (RANS) based 3D hydrodynamics and sediment transport model was developed for Bulles experiments using the open-source solver Telemac-Mascaret. This model was found to capture the phenomenon satisfactorily but at a relatively lower computational cost. The substantial reduction in computational cost is important, because at this point it impossible to conduct accurate Large Eddy Simulations (LES) of flows at the scale of real rivers. Thus it becomes important to evaluate if RANS based models can capture a complex phenomenon, and if this is the case to what extent? The RANS model was then used to study the impact of Bulle-Effect on morphodynamics of the diversion. The separation of the flow from the left-bank of the lateral-channel was found to result in formation of a scour-hole under the high-flow zone and subsequent deposition sediment under the flow-recirculation. The impact of the change in morphology of the channel on Bulle-Effect was also analyzed. The findings of this dissertation not only add to the fundamental understanding of an important phenomenon in nature, these also provide insights that will help in optimal design of engineered diversions and other facilities where vorticity and secondary-flow driven sediment/particle transport occurs. Based on disproportionately high sediment transported into the diversions of the Yellow River, China, Canal del Dique on the Magdalena River, Columbia etc., it can be conjectured that the Bulle-Effect plays a major role at the aforementioned diversions. Thus, in the future numerical simulations of real-world diversions should be conducted ( in conjunction with field measurements) in order to study the flow-structure and sediment distribution pattern at diversions, and to understand the extent to which the Bulle-Effect impacts real-world diversions

SEDIMENT TRANSPORT AND CHANNEL MORPHOLOGY OF A NATURAL AND A LEVEED ALLUVIAL RIVER

Alluvial rivers are shaped by interactions of flow and sediment transport. Their lower reaches to the world’s oceans are highly dynamic, often presenting engineering and management challenges. This thesis research aimed to investigate channel dynamics and sediment transport in a natural river and a highly engineered river in South Louisiana, in order to gain much-needed science information for helping develop sustainable practices in river engineering, sediment management, and coastal restoration and protection. Especially, the thesis research examined (1) riverbed deformation from bank to bank in the final 500-km reach of the Mississippi River, (2) bed material transport at the Mississippi-Atchafalaya River diversion, and (3) long-term and short-term flood effects on the morphological changes of the Amite-Comite River confluence. The research employed morphological, hydrodynamic, and geospatial modeling and analysis. The research found that from 1992 to 2013 the lowermost Mississippi River channel trapped 337 × 106 m3 sediment, equal to about 70% of riverine sand input from the upstream channel. The finding rejects the initial hypothesis that the highly engineered Mississippi River acts as a conduit for sediment transport. Sediment deposition mainly occurred in the immediate channel downstream of the Mississippi-Atchafalaya River diversion and the reach between RK 386 and RK 163, reflecting flow reduction and backwater influences. The bed material transport assessment revealed that in the recent decade the engineering-controlled Mississippi-Atchafalaya River diversion showed a slight disproportional transport of bed material loads. On average 24% of the Mississippi River was diverted into the Atchafalaya, but only 22% of bed material loads moved into the diversion outflow channel (i.e. 47 MT out of 215 MT). The confluence of Amite and Comite River continuously migrated about 55 m downstream between 2002 and 2017. Sediment deposition on the main channel side of the confluence mouth bar is the major driver for the confluence migration. Regression analysis shows that the increase rate of the vegetated area of the bar is highly related to the days of moderate floods. Short-term Laser scanning measurements reveal that a single flood with the intensity close to a moderate flood could double the projected surface area of the mouth bar and increased its volume by 68%. Overall, the thesis research shows the complexity of sediment transport in the lower reach of a large alluvial river, in that distinctive bed deformation can occur in different reaches because of flow deduction and backwater effects. Our study is the first try of estimating bed material load at a largely controlled bifurcation based on a simple, well-established bed material transport model. The study also highlights the importance of episodic floods on the evolution and migration of a river confluence

From meander bend to oxbow lake: morphodynamics and sedimentology of chute cutoffs

Chute cutoffs are common features of meandering channels. The development of a chute cutoff locally shortens and straightens a meandering river channel, excavating a large volume of floodplain sediment as the chute channel deepens and widens. Bar development at the upstream and downstream ends of the cutoff channel leads to abandonment of the bend and formation of an oxbow lake, which, together with oxbow lake sedimentation, contributes to the production of a complex, highly three-dimensional floodplain sedimentary architecture. Moreover, the oxbow lakes that result from meander cutoffs enhance habitat diversity within riparian corridors. Thus, chute cutoffs play an integral role in the geomorphology, sedimentology, and ecology of the channel-floodplain system of meandering rivers. The primary objective of this thesis is to advance understanding of chute cutoff morphodynamics through a process-based interpretation of the co-evolution of morphology, flow structure, and sedimentology in chute cutoff channels prior to bend abandonment. This objective is achieved through a combined field and laboratory approach, using observations from a detailed field study of two chute cutoffs at Mackey Bend, Wabash River, IL/IN, USA, and results from laboratory experiments in a physical model of a chute cutoff system. Analysis of the morphologic evolution and sedimentology at the field site (Chapter 4) indicates that chute cutoffs undergo an initial phase of rapid widening, during which sediment is deposited at the cutoff mouth. This period of rapid chute widening gradually leads to a phase of bar deposition in the upstream limb of the bend and along the inner bank of the chute channel, and reorganization of sediment deposited at the cutoff mouth. The compound bars at Mackey Bend are constructed by deposition of unit bars and dunes, as well as deposition of fine grained sediment during periods of high backwater caused by high flow on the nearby Ohio River. Flow structure associated with the two chute cutoffs is characterized by: (1) deceleration of flow (and possible flow stagnation) in the main channel, moving from upstream to downstream past the entrance to the chute cutoff channel; (2) strong curvature of flow into the chute cutoff channel, which induces strong secondary circulation and advection of the core of high velocity toward the outer bank of the cutoff channel; (3) flow separation along the inner bank of the cutoff channel(s); (4) convergence of flows from the cutoff channel and the main bend at the downstream end of the chute cutoff channel (cutoff mouth), which promotes the development of counter-rotating helical cells in the converging flows; (5) flow stagnation and superelevation of the water surface at the upstream junction corner of the cutoff mouth; and (6) deceleration of flow, and possible flow separation, at the downstream junction corner of the cutoff mouth. The hydrodynamics of chute cutoffs were also investigated in a physical model with a rectangular channel geometry, simplified planform shape, and immobile bed and banks. In this physical model, the cutoff channel was equal to the width of the main channel. Experimental results show that the three-dimensional structure of flow is analogous to a scenario in which the upstream limb of the bend is completely plugged with sediment. In this situation, all of the discharge is routed through the cutoff channel, and a large, vertically-oriented gyre develops in the downstream limb of the bend, similar to the pattern of flow recirculation that occurs in a side embayment along an open channel. Areas of high turbulent kinetic energy are located along: (1) the shear layer between flow entering the cutoff channel and near-stagnant water in the upstream limb of the bend, (2) the boundary of the flow separation zone in the cutoff channel, and (3) the shear layer between flow moving out of the cutoff channel and stagnant, or slowly moving, flow within the downstream limb of the bend. Values of turbulent kinetic energy in the abandoned bend, particularly for the case in which most of the discharge is moving through the cutoff channel, are much lower than those in a meander bend with no cutoff channel. The integrated results from field and laboratory studies allow formulation of a model of chute cutoff morphodynamics, where the entrance and exit of a chute cutoff channel behave as a bifurcation and confluence, respectively, and bar development primarily occurs: (1) in the upstream limb of the main channel, (2) along the inner bank of the cutoff channel, and (3) in the mouth of the cutoff channel. Once the upstream limb of the bend is completely plugged with sediment and no flow moves through the bend, the side embayment model describes the morphodynamics of plug bar deposition, where sediment is entrained into the downstream limb of the bend by a large-scale gyre. The bend becomes an oxbow lake once the downstream limb of the bend is completely sealed with sediment

Dynamics and Morphodynamic Implications of Chute Channels in Large, Sand-Bed Meandering Rivers

Chute channel formation is a key process in the transition from a single-thread meandering to a braided channel pattern, but the physical mechanisms driving the process remain unclear. This research combines GIS and spatial statistical analyses, field survey, Delft3D hydrodynamic and morphodynamic modelling, and Pb-210 alpha-geochronology, to investigate controls on chute initiation and stability, and the role of chute channels in the planform dynamics of large, sand-bed meandering rivers. Sand-bed reaches of four large, tropical rivers form the focus of detailed investigations; the Strickland and Ok Tedi in Papua New Guinea, the Beni in Bolivia, and the lower Paraguay on the Paraguay/Argentina border. Binary logistic regression analysis identifies bend migration style as a key control on chute channel initiation, with most chute channels forming at bends that are subject to a rapid rate of extension (elongation in a direction perpendicular to the valley axis). Bend extension rates are shown to track variation in potential specific stream power, such that reaches and sub-reaches of the rivers studied fit within a planform continuum expressed though increasing bend extension rates and chute initiation frequency, and driven by increasing stream power relative to bedload calibre. Field observations of point bar geomorphology and vegetation dynamics illustrate the importance of rapid bend extension in forming wide sloughs between scroll bars that are aligned with the direction of over-bar flow, and in breaking the continuity of vegetation encroachment on point bars. Bathymetric surveys and Delft3D simulations for the Strickland River provide insight into flow and sediment division at bifurcate meander bends. Coupled with GIS analyses, these simulations show that stable chute channels have higher gradient advantages than chute channels subject to infill, but that upstream and downstream changes in bend orientation can also influence chute stability. The process of bend extension is typically associated with an increase in the chute gradient advantage, further elucidating the role of bend migration style in chute stability. At the reach scale, rivers with higher sediment loads (Qs/Q) are characterised by higher rates of chute infill. Strickland River floodplain sedimentation rates derived through Pb-210 alpha-geochronology are substantially higher adjacent to single-thread bends than adjacent to bifurcate bends, potentially due to an observed increase in channel capacity (and reduction in floodplain inundation frequency) associated with bend bifurcation. Further research is needed to determine whether this observation is significant in light of high uncertainty in the spatial variability of sedimentation rate estimates, but the data presented highlight a need for carefully considered stratified sampling approaches in floodplain coring campaigns, and illustrate the complexity of possible sediment dispersal mechanisms, and associated ecological responses. GIS analysis of the response of the Ok Tedi in Papua New Guinea to direct addition of mine tailings elucidates interplay between channel steepening due to the propagation of a tailings sediment slug, and mid-channel bar formation induced by the increased sediment load, with associated topographic forcing of bend and chute development. A temporal pattern of increased chute initiation frequency on the Ok Tedi mirrors the inter- and intra-reach spatial pattern of chute initiation frequency on the Paraguay, Strickland and Beni Rivers, where increased stream power is associated with increased bend extension and chute initiation rates. The process of chute formation is shown to be rate-dependent, and the threshold value of bend extension for chute initiation is shown to scale with reach-scale stream power, reminiscent of slope-ratio thresholds in river avulsion. However, Delft3D simulations suggest that chute formation can exert negative feedback on shear stress and bank erosion in the adjacent mainstem bifurcate, such that the process of chute formation is also rate-limiting. Chute formation is activated iteratively in space and time in response to changes in river energy, selectively targeting sites of greatest change, and thereby mediating the river response

Modélisation de l'évolution morphodynamique des dunes sous-marines

Sand dunes are ubiquitous beforms in nature within subaqueous environments. Understanding dune evolution is important issue to accurately predict the ow circulation, sediment uxes and bathymetric variations in sandy subaqueous environments. Sand dunes may pose a significant risk for offshore activities in coastal environments, especially with the growing development of renewable marine energy, for navigation or the offshore industry. Although sand dunes represent a great scientific and operational interest, their evolution is still poorly understood due to their complex behavior. The aim of the thesis work was to study the physical processes driving the evolution of subaqueous sand dunes and to understand their in situ dynamics within tidal environments. First, a numerical model was employed to simulate sand dunes under stationary current conditions. The simulations reproduced the morphodynamic evolution of a slightly perturbed bed until a steady sand dune field in equilibrium with the ow. The results offered a deeper understanding of the physical processes driving the bed evolution to equilibrium. Second, an array of in situ measurements was carried out into the Arcachon inlet, in southwest France, to study the dynamics of tidal sand dunes. For the first time their asymmetry and migration rates were linked to the sediment uxes residuals on a spring-neap tidal cycle. Finally, the numerical model was adapted both to simulate the dynamics of tidal sand dunes, and generate bedforms of the same order of magnitude as the in situ dune-superimposed ripples starting from a at bed. These results open promising perspectives for the development of a numerical tool capable of predicting the behavior of sand dunes within tidal environments.Les dunes de sable sont des formes très présentes en milieu marin. Comprendre l'évolution des dunes est un enjeu important pour prévoir les caractéristiques de l'écoulement, les flux sédimentaires, et les variations de la bathymétrie. Les dunes sous-marines représentent un risque pour les activités humaines, a fortiori avec l'intérêt croissant pour les énergies marines renouvelables, pour la navigation, ou l'industrie offshore. Bien que la connaissance des dunes représente un intérêt scientifique et opérationnel de premier ordre, les processus physiques conduisant leur évolution sont toujours mal compris. En outre, la prévision de leurs caractéristiques géométriques et de leur dynamique basée essentiellement sur des formules empiriques reste peu précise. Dans ce travail de thèse, un modèle numérique est d'abord utilisée pour modéliser les dunes soumises à un écoulement stationnaire. Les simulations reproduisent l'évolution d'un fond faiblement perturbé jusqu'à un champ de dunes en équilibre avec l'écoulement et apportent des connaissances approfondies sur les processus physiques mis en jeu. Ensuite, les résultats d'un ensemble de campagnes de mesures réalisées dans la passe sud du bassin d'Arcachon permettent d'étudier la dynamique des dunes tidales in situ et relier leur asymétrie et leur migration aux résiduels de transport sédimentaire. Enfin, l'application du modèle numérique avec les conditions de forçages extraites des campagnes de mesures permet de reproduire la dynamique des dunes tidales ainsi que la génération de rides d'un ordre de grandeur comparable aux rides surimposées observées in situ. Ces résultats ouvrent des perspectives intéressantes en vue du développement d'un modèle opérationnel de prévision de la dynamique des dunes tidales

Modélisation de la rigidité et de la perméabilité des grands troncs artériels

Introduction: Les pathologies cardio-vasculaires sont une cause dominante de mortalité dans les sociétés occidentales. Les mathématiques et les progrès de l’ingénierie, en sus de l’approfondissement de la physiologie et physiopathologie, sont de plus en plus fréquemment utilisés pour venir à bout de ce fléau. Méthodes: Nous travaillons au développement et à la validation de modèles théoriques décrivant la filtration des macromolécules à travers les différentes couches de la paroi artérielle. À ces fins, nous avons étudié et caractérisé certaines composantes des parois de l'aorte. Aussi, en guise de validation des modèles de filtration, dans des situations contrôlées, nous étudions la distribution de l’albumine exogène marquée du compartiment vasculaire à travers les différentes couches de la paroi d’aortes thoraciques provenant de lapins normaux. Pour ce faire, nous utilisons la microscopie à fluorescence et l'immunocytochimie en microscopie électronique. Enfin, à l'aide de modèles mathématiques, nous étudions les éléments susceptibles d’expliquer le phénomène de rigidité des gros troncs artériels. Résultats: Nous avons étudié et caractérisé une partie de la couche de surface des cellules endothéliales et l'endothélium luminal aortique. La limitante élastique interne a également été bien étudiée, en particulier la taille des pores de cette dernière ainsi que l'orientation des fibres d'élastine qui la compose. Les résultats préliminaires montrent que les fibres d'élastine de la limitante élastique interne sont majoritairement orientées de manière parallèle à la direction du flot. Au contraire, nos premières observations montrent que les fibres d'élastine de la média sont orientées de manière perpendiculaire à la direction du flot luminal. Enfin, le système vasa vasorum de l’adventice de l’aorte thoracique a été étudié. À l'aide de moulage de l'aorte et d'études en microscopie électronique, nos résultats préliminaires montrent que la densité des vasa vasorum de l'aorte thoracique est plus grande dans sa paroi postérieure que dans sa paroi antérieure. Pour terminer, nous avons approfondi le rôle des érythrocytes dans la filtration des protéines à travers les parois artérielles en déterminant un coefficient de partition des protéines de 0,204 +/- 0,017 entre l'intérieur des érythrocytes et le plasma. Conclusions: Les résultats morphologiques obtenus et l’analyse préliminaire des paramètres physiologiques examinés rejoignent certaines observations disponibles de la littérature. Ces résultats permettront vraisemblablement d'améliorer les modélisations mathématiques des phénomènes de filtration à travers les parois des grands troncs artériels et du phénomène de la rigidité artérielle. De plus, nous présentons le développement d’une technique de validation quantitative des modèles de filtration

Microparticules magnétiques thérapeutiques pour la chimio-embolisation ciblée du foie

RÉSUMÉ Cette thèse présente un vecteur thérapeutique pour le traitement des tumeurs du foie basé sur une nouvelle méthode de ciblage magnétique. Le carcinome hépatocellulaire (CHC) est le cancer le plus fréquent dans le foie. Il est la troisième cause de mortalité reliée à un cancer. Sa fréquence augmente à travers le monde et le pronostic reste sombre (mortalité dans les 3 à 6 mois) malgré de multiples recherches. Environ 70 % des patients ne peuvent recevoir que des traitements palliatifs et la chimio-embolisation demeure l’approche la plus efficace. Cette procédure combine deux techniques: la chimiothérapie avec l’injection par cathéter d’un agent anticancéreux et l’embolisation des vaisseaux sanguins par des microparticules provoquant une ischémie de la tumeur. Afin de maximiser son efficacité et de limiter ses effets secondaires, ce traitement doit être ciblé au niveau de la tumeur. Cependant, le ciblage est actuellement limité par le positionnement du cathéter à plusieurs bifurcations des vaisseaux sanguins en amont de la tumeur. Comme la distribution des agents chimio-embolisants n’est pas contrôlée, il en résulte une atteinte des cellules saines. La navigation par résonance magnétique (‘magnetic resonance navigation’ (MRN)) a été récemment proposée comme une nouvelle méthode de ciblage magnétique des tumeurs. Elle consiste à contrôler la direction d’un corps ferromagnétique en temps réel selon une trajectoire prédéterminée dès son injection dans un réseau vasculaire jusqu’à la zone d’intérêt grâce à un appareil d’imagerie par résonance magnétique (IRM). La navigation dépend du gradient magnétique, du volume et de la magnétisation à saturation (Ms) du dispositif thérapeutique ainsi que des paramètres physiologiques du réseau vasculaire ciblé. Deux bobines de gradient de 400 mT m-1 sont placées dans l’IRM afin de guider des corps à l’échelle micrométrique. L’hypothèse de recherche de cette thèse est qu’il est possible de réaliser un vecteur thérapeutique compatible avec les contraintes de la chimio-embolisation du foie et de la MRN au niveau de l’artère hépatique pour cibler les lobe gauche/droit du foie. Ce vecteur, appelé ‘therapeutic magnetic microcarriers’ (TMMC), est chargé avec un agent anticancéreux et des nanoparticules magnétiques. Il a été conçu en prenant en considération les paramètres physiologiques du lapin, modèle animal choisi pour évaluer la MRN in vivo.----------ABSTRACT The proposed project introduces a therapeutic vector for the liver tumor treatment based on a new magnetic targeting strategy. Hepatocellular carcinoma (HCC) is the most common liver tumor and it is the third cause of cancer-related death. The incidence of HCC is increasing worldwide and its prognostic remains poor (death within 3 to 6 months) despite intensive researches. Approximately 70% of the patients can receive only palliative treatments and chemoembolization is the most efficient approach. This intervention combines two treatment modalities: the chemotherapy with the injection of an antitumor drug, and the embolization of the blood vessels with microparticles, inducing an ischemia of the tumor. To optimize the efficiency and to reduce the secondary effects, this treatment should be targeted on the tumor. However, this targeting is actually limited by the placement of the catheter used for the injection of the cytotoxic agent in the blood vessels at several bifurcations upstream of the tumor. Since the distribution of the chemoembolizing agent cannot be controlled, healthy cells are also affected by the treatment. Magnetic resonance navigation (MRN) has been recently proposed as a new method for the magnetic targeting of tumors. This method aims at controlling the direction of a ferromagnetic body in real time along a pre-planned trajectory from its release in the vascular network to the region of interest with a magnetic resonance imaging (MRI) scanner. MRN depends on the magnetic gradient, the volume and the saturation magnetization (Ms) of the therapeutic device and the physiological properties of the vascular network being targeted. An insert of gradient coils of 400 mT m-1 is placed in the MRI system to steer micro scale devices. The hypothesis of this thesis is that it is possible to design a therapeutic vector compatible with the constraints of liver chemoembolization and MRN in the hepatic artery to target the right/left lobe of the liver. This vector, referred to as therapeutic magnetic microcarriers (TMMC) is loaded with an antitumor drug and magnetic nanoparticles. It was designed by taking into consideration the rabbit physiological parameters, the rabbit being the animal model chosen for the in vivo MRN experiments