ED Mathématiques et Informatique
Numerical Study of liver tumor ablation by electroporation
by Olivier SUTTER (IMB - Institut de Mathématiques de Bordeaux)
The defense will take place at 14h00 - à déterminer Centre Inria de l'université de Bordeaux 200 Av. de la Vieille Tour, 33405 Talence
in front of the jury composed of
- Clair POIGNARD - Directeur de recherche - Centre Inria de l'Université de Rennes - CoDirecteur de these
- Szopos MARCELA - Professeure des universités - Université Paris Cité - Rapporteur
- Baudouin DENIS DE SENNEVILLE - Directeur de recherche - CNRS, Institut de Mathématiques de Bordeaux, INRIA - Directeur de these
- François CORNELIS - Professeur des universités - praticien hospitalier - Memorial Sloan Kettering Cancer Center - Rapporteur
- Muriel GOLZIO - Directrice de recherche - Institut de pharmacologie et de biologie structurale (IPBS) / CNRS UMR 5089 - Examinateur
- Anthony DOHAN - Professeur des universités - praticien hospitalier - Assistance Publique Hôpitaux de Paris (APHP) / Université Paris Centre - Examinateur
- Emeline RIBOT - Chargée de recherche - Centre de résonance magnétique des systèmes biologiques (CRMSB) / CNRS UMR5536 - Examinateur
- Damien VOYER - Enseignant-Chercheur (ENAC, ISAE) - EIGSI, École d'ingénieurs généralistes - Examinateur
Irreversible electroporation (IRE) is a non-thermal ablation technique currently employed as a “last-resort” curative option for deep-seated cancers that are surgically unresectable and unsuitable for thermal ablation due to their proximity to vital anatomical structures. The principle of IRE involves delivering multiple short high-voltage electric pulses via several needle electrodes (at least three, but often four to six) percutaneously inserted around the tumor under imaging guidance. The repetition of pulses induces persistent permeabilization of tumor cell membranes, leading to cell death through apoptosis without damaging the extracellular matrix. Despite this unique mechanism, the clinical efficacy of IRE remains lower than that of other treatment options and several challenges must be addressed to improve clinical outcomes. First, IRE requires precise placement of multiple electrodes around the target tumor, which is challenging to reach percutaneously because of its deeply embedded location in the liver. The electrode implantation scheme must be optimized to ensure that the electric field (EF) adequately covers the entire tumor. However, treatment efficacy is currently assessed only retrospectively and no peri-operative evaluation criteria are currently available to assist interventional radiologists performing this procedure. Second, because the treated tissue is inherently a heterogeneous conductive medium, the composition of the tumor, the underlying organ and the presence of adjacent structures all influence EF distribution and magnitude, and should therefore be integrated into numerical modeling. Lastly, since tumor recurrence remains frequent after IRE, the post-operative follow-up, based on magnetic resonance imaging (MRI), should be better understood and correlated with per-operative data. The objective of this thesis was to adapt and refine numerical modeling of IRE for peri-operative assessment of liver tumor ablation. Across four complementary studies, we propose here numerical methods based on advanced image-registration strategies, mathematical modeling, and simulations informed by clinical outcomes to progress toward a numerically assisted evaluation of IRE efficacy.
ED Sciences et environnements
Microplastic Transport and Trapping in a Highly Turbid, Tide-Dominated Estuary
by Betty John KAIMATHURUTHY (Environnements et Paléoenvironnements Océaniques et Continentaux)
The defense will take place at 14h00 - Salle Univers Bâtiment B18N Allée Geoffroy Saint-Hilaire, CS 50023, 33615 Pessac
in front of the jury composed of
- Isabel JALON ROJAS - Chargée de recherche - CNRS - Directeur de these
- Damien SOUS - Maître de conférences - Université de Pau et des Pays de l'Adour - SIAME - CoDirecteur de these
- Elisa Helena Leão FERNANDES - Full professor - Universidade Federal do Rio Grande - Rapporteur
- Manuel DIEZ MINGUITO - Associate Professor - Universidad de Granada - Rapporteur
- Alexandra TER HALLE - Directrice de recherche - CNRS - Examinateur
- Aldo SOTTOLICHIO - Professor - Université de Bordeaux - Examinateur
Microplastics are an emerging pollutant in aquatic systems, with estuaries acting as key zones for their retention and transformation. However, limited field observations, complex estuarine hydrodynamics and diverse particle properties hinder a comprehensive understanding of microplastic transport and fate, limiting accurate risk assessment and evaluation of environmental impacts. The objective of this work is to better understand the physical processes governing the transport and trapping of microplastics in macrotidal turbid estuaries, using the Gironde estuary (SW France) as a case study. The methodology of this work is mainly based on a hydro-sedimentary numerical model coupled with a Lagrangian particle tracking model. This approach is complemented by in-situ observation data. A comprehensive review of process-based modelling approaches used to study microplastic dynamics in estuaries was first conducted to assess various parameterization strategies, identify key challenges, and offer recommendations and future directions to advance microplastic modelling strategies in estuaries. Building on insights from this review, the relative influence of estuarine physical processes on microplastic transport was examined through sensitivity scenarios using different release configurations. The results identify the shoreline interaction by beaching–refloating dynamics as a key process for buoyant particles, while resuspension and vertical mixing modulate the transport and vertical distribution of non-buoyant particles. Microplastic-sediment interactions, such as flocculation and temporary trapping in bottom sediments, play an important role in enhancing particle retention within the estuary. Model results also show that hydrodynamic processes alone can significantly trap microplastics, with seasonal variability modulating the intensity and location of trapping. Elevated river discharge during the spring season enhances seaward transport, particularly for buoyant particles, whereas in summer, microplastics are more likely to be retained, with denser particles accumulating near the estuarine turbidity maxima (ETM) in the tidal rivers. This accumulation forms a water-column estuarine microplastic maximum (EMPM), sustained by net upstream transport driven by tidal pumping. In-situ observations in the water column support these findings, confirming the presence of strong near-bottom microplastic concentrations in summer in the Garonne tidal river, particularly during strong flood and ebb current velocities, with a dominance of high-density fibrous particles. Model simulations also indicate that floating particles are consistently trapped along a frontal line near the main channel, generating a surface EMPM. In the upper estuary, this line of particle accumulation follows the primary convergence zone produced by the combined effects of tidal currents and estuarine bathymetry. However, in the middle estuary, the accumulation line shifts to a secondary convergence zone due to the combined impact of morphological features and the alternance between convergence and divergence patterns over the tidal cycle. Sensitivity tests confirm that baroclinic effects play a significant role in shaping frontal convergence, with sediment-induced water density modulating its strength. Overall, the results highlight that tide-dominated, highly turbid estuaries act as efficient microplastic retention zones due to the combined influence of tidal hydrodynamics, sediment-microplastic interactions, and morphological features.