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Exploitation des effets électro-optiques pour la sécurité en IRM : applications des liaisons optiques pour des capteurs RF endoluminaux et des sondes de mesure du TAS

Isabelle Saniour 1 
1 RMN et optique : De la mesure au biomarqueur
CREATIS - Centre de Recherche en Acquisition et Traitement de l'Image pour la Santé
Abstract : The recent advancement in MRI systems and the increase of the static magnetic field strength were accompanied by a strong concern about the effect of RF electromagnetic fields on patients. The effect can be increased by the use of conductive elements inside the volume coil as in the case of endoluminal coils used to analyze digestive walls. These coils lead to an increase of the local SAR which is induced by RF electric field in the presence of the coaxial cable connecting the coil to the MR system, resulting in strong local heating. Giving that these coils have the potential to present a real benefit to the patient, it worth to overcome these limitations. Accordingly, the first objective of the thesis is the development of a fully optical endoluminal receiver coil. An optical active detuning system has been developed and characterized. The NMR images show a signal-to-noise ratio distribution similar to that obtained with conventional detuning techniques, thus validating the efficiency of the optical detuning. Concerning the electro-optical conversion and the optical transmission of the NMR signal, experiments were performed to overcome constraints related to the use of waveguide for electro-optical conversion by Pockels effect. Moreover, the importance of monitoring global and local SAR during MRI exams remains a need which is not limited only to the endoluminal coils. The second objective of the thesis is then the experimental validation of an electro-optical probe for real-time measurements of RF electric field. This probe can measure the RF electric field in air and in biological media at 3 T and 4.7 T MRI systems and allows the estimation of the local SAR
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Isabelle Saniour. Exploitation des effets électro-optiques pour la sécurité en IRM : applications des liaisons optiques pour des capteurs RF endoluminaux et des sondes de mesure du TAS. Ingénierie biomédicale. Université de Lyon, 2017. Français. ⟨NNT : 2017LYSE1330⟩. ⟨tel-01787691⟩

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