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This work presents the project that I realized during my four months internship inside the
Courtois NeuroMod project, in Montreal, from February to June 2022. The Courtois project on neuronal modeling (CNeuroMod) aims to collect 500h of functional neuroimaging data per subject, on 6 subjects over a period of 5 years using a range of natural stimuli. This large multimodal data set is then used to train artificial neural networks that mimic human behavior and brain activity in multiple tasks, following a brain-augmented learning paradigm. One of the future projects of the lab is to explore the field of robotics and, more specifically, to embed brain-augmented models in small robots, trained in real-world conditions. The first part of this project presents the development of an Application Programming Interface (API) to control a commercial robot, called the Cozmo robot. The final goal is to be able to control the robot from inside a Magnetic Resonance Imaging (MRI) scanner with a video game controller. Since the lab develops deep learning architectures for Reinforcement Learning (RL) tasks, the developed API also provides a framework for RL with the robot. The API is based on an existing interface, and is designed to provide a simple user interface. This API is then used to deploy a control task in a MRI machine, by integrating the API into the software framework already in place for the experiments within the NeuroMod project. As the robot can be located anywhere in the building, the implementation manages data transfers between machines so that the control can be done in real time and data of interest can be retrieved in addition to those acquired by the MRI. A human subject is finally able to control a remote robot using a joystick, from inside an MRI machine acquiring its brain data. An automatic tracking system of the robot is also developed.

API, MRI, Robotics, Neuroscience --- Ingénierie, informatique & technologie > Multidisciplinaire, généralités & autres

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The locus cœruleus (LC) is a small noradrenergic nucleus of high interest in neuroscience. As the main source of noradrenaline in the brain, it is involved in numerous cognitive functions such as arousal, attention and memory. In addition, previous studies have emphasised its relationship with the progression of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. The visualisation of the LC in magnetic resonance imaging (MRI) is realised through so-called neuromelanin-imaging in which magnetisation transfer (MT) effects are thought to be the main source of contrast. However, current researches insufficiently characterise the underlying contrast generation mechanisms given the poor understanding in the LC tissue properties. Efficiently visualising the locus coe ruleus is therefore a challenging process that requires further investigation.

The aim of this thesis is to provide an efficient tool for better understanding the underlying contrast mechanisms in the LC and thereby optimising its visualisation through multi-compartment spoiled gradient echo (SPGR) imaging. Firstly, the simulation of such a sequence through the extended phase graph with exchange (EPG-X) framework is performed in order to determine optimal sequence parameter values. After an experimentation phase, the outcomes are validated against the developed model. Simulation suggests that an optimal contrast can be achieved by maximising the power of the excitation pulse. It is expected that the use of optimal sequences compared to the one currently played out at the Wellcome Centre for Human Neuroimaging (WCHN) would improve the LC visualisation. Nonetheless, the lack of robust validation prevent the generalisation of these observations. Secondly, the SPGR model is extended by including a saturation pre-pulse for amplifying the MT effects. The contrast optimisation is realised through simulation according to the same formalism as previously while accounting for the MT pre-pulse. Optimal parameter values suggest that an improvement is achievable regarding the MT-weighted sequence currently played out through the maximisation of the power and the off-resonance frequency of the MT pulse as well as the time delay between the saturation and excitation pulses. Unfortunately, no validation was achievable for this configuration which should be investigated in future researches.

Because of the lack of knowledge about the contrast mechanisms in the LC, the optimisation of an MRI sequence effectively targeting the LC is complex. Therefore, due to the numerous parameters involved and the poor confidence regarding their impact, future studies should focus on a better characterisation of this structure and the inherent contrast mechanisms.

MRI --- Locus cœruleus --- Magnetisation transfer --- SPGR --- Contrast --- Ingénierie, informatique & technologie > Multidisciplinaire, généralités & autres

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Het doel van deze eindverhandeling bestond erin om een phased array van oppervlaktespoelen voor MRI te bestuderen, simuleren en ontwikkelen. Simulatie door middel van de Finite Difference - Time Domain methode (FDTD) wordt besproken, en een methode om geconcentreerde elementen te combineren met een niet reflecterende simulatie grenszone (PML) werd opgesteld. De benodigdheden om zo'n array te bouwen worden besproken en de beperkingen geanalyseerd vanuit meerdere standpunten, zoals veiligheid en kostprijs. De oplossing voor enkele courante problemen zoals ontkoppeling tussen spoelen en mantelstromen wordt beschreven. Ook wordt theoretisch een opstelling besproken voor beeldvorming met Xenon-129, samen met enkele technieken om de prestaties te meten zonder een MRI scanner beschikbaar te hebben. The goal of this thesis was the analysis, simulation and development of a phased array of surface coils for MRI. Simulation using the Finite Difference - Time Domain method is analysed, and a method to combine a perfectly matched layer (PML) with lumped elements is introduced. The requirements for an array and the practical limitations are analysed from several perspectives, such as safety and cost. The solution to several common problems, like decoupling between coils and common-mode currents, are described. Finally a theoretical array for imaging using Xenon-129 was proposed together with techniques to test it without having an MRI scanner available.

Analoge elektronica - analog electronics. --- FDTD. --- Hyperpolarisatie. --- MRI. --- Magnetische resonantie. --- Oppervlaktespoel. --- Phased array.

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Introduction – Les maladies cardiovasculaires sont devenues un problème majeur de santé publique. Dans certains cas, la mise en place d'un pacemaker devient une nécessité. De plus, il existe une évolution croissante de l'imagerie par résonance magnétique (IRM) ainsi que du nombre de patients porteurs d'un pacemaker. 50 à 75 % des patients avec stimulateur cardiaque devront avoir une IRM durant leur vie. Le problème lié à l'IRM est la présence du champ magnétique. Des précautions sont à prendre dans le cadre de la prise en charge de ces patients venant passer une IRM.
Méthodes - Cette étude s'est déroulée de décembre 2017 à juillet 2018. Elle consistait en une approche pré-expérimentale mixte dans le service d'IRM du CHR de Liège. Elle a débuté par une analyse rétrospective de l'année 2016 afin de mettre en évidence l'incidence de patients porteurs d'un pacemaker en IRM et combien d'entre eux ont été refusés. Une analyse sur le terrain de l'application de la procédure contenant les indications pour la prise en charge des patients porteurs d'un pacemaker lors d'une IRM a été réalisée. Ensuite, des entretiens ont été réalisés afin d'évaluer les connaissances du personnel d’IRM sur la procédure ainsi que la satisfaction de ceux-ci par rapport à la situation actuelle, les contraintes et leurs suggestions d'amélioration. Suite aux résultats, des séances d'information ont été mises en place. Elles faisaient intervenir le chercheur et le responsable qualité du service d'IRM. Après ses séances, une nouvelle mesure de l'application de la procédure a été réalisée.
Résultats – L'analyse rétrospective a mis en évidence une grande proportion de patients porteurs d'un pacemaker venus en IRM et chez qui on a refusé de réaliser l'examen. L'analyse quantitative et les entretiens ont démontré des lacunes dans la connaissance de la procédure. Les séances d'information ont eu un taux de participation de 66,67 % du personnel du service de résonance magnétique. Malgré quelques lacunes persistantes, l'analyse de l'application de la procédure post-intervention a montré de grandes améliorations dans la prise en charge des patients porteurs d'un pacemaker en IRM.
Conclusion – Cette étude démontre une amélioration de la prise en charge des patients porteurs d'un pacemaker se présentant en IRM au CHR de la Citadelle. Néanmoins, le faible échantillon de cette étude ne nous permet pas de la généraliser. Il faudrait réaliser à nouveau une étude sur une plus grande période afin de pouvoir valider les résultats.

Pacemaker --- MRI --- Improvement --- Patient Safety --- Precaution --- Pacemaker --- IRM --- Amélioration --- Sécurité du patient --- Précaution --- Sciences de la santé humaine > Santé publique, services médicaux & soins de santé

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Magnetic Resonance Angiography. --- Image Enhancement. --- Image Processing, Computer-Assisted. --- Liver Transplantation --- Kidney Transplantation --- Image Quality Enhancement --- Enhancement, Image --- Enhancement, Image Quality --- Enhancements, Image --- Enhancements, Image Quality --- Image Enhancements --- Image Quality Enhancements --- Quality Enhancement, Image --- Quality Enhancements, Image --- Perfusion Magnetic Resonance Imaging --- Perfusion Weighted MRI --- Angiography, Magnetic Resonance --- MRI Angiography --- Angiographies, MRI --- Angiographies, Magnetic Resonance --- Angiography, MRI --- MRI Angiographies --- MRI, Perfusion Weighted --- Magnetic Resonance Angiographies --- radiography. --- Analysis, Computer-Assisted Image --- Computer-Assisted Image Analysis --- Computer-Assisted Image Processing --- Image Analysis, Computer-Assisted --- Image Reconstruction --- Computer Assisted Image Analysis --- Computer Assisted Image Processing --- Computer-Assisted Image Analyses --- Image Analyses, Computer-Assisted --- Image Analysis, Computer Assisted --- Image Processing, Computer Assisted --- Image Reconstructions --- Reconstruction, Image --- Reconstructions, Image --- Diagnostic Imaging --- Data Compression --- Multimodal Imaging --- Biomedical Image Processing --- Digital Image Processing --- Medical Image Processing --- Image Processing, Biomedical --- Image Processing, Digital --- Image Processing, Medical --- Image Processings, Medical --- Medical Image Processings --- Processing, Biomedical Image --- Processing, Digital Image --- Processing, Medical Image --- Processings, Digital Image --- Processings, Medical Image --- Magnetic Resonance Angiography --- Image Enhancement --- Image Processing, Computer-Assisted --- radiography --- Grafting, Kidney --- Renal Transplantation --- Transplantation, Kidney --- Transplantation, Renal --- Kidney Grafting --- Kidney Transplantations --- Renal Transplantations --- Transplantations, Kidney --- Transplantations, Renal --- Kidney --- Grafting, Liver --- Hepatic Transplantation --- Liver Transplant --- Transplantation, Hepatic --- Transplantation, Liver --- Hepatic Transplantations --- Liver Grafting --- Liver Transplantations --- Liver Transplants --- Transplant, Liver --- Liver --- transplantation