Adaptation des paramètres temporels en imagerie par résonance magnétique en fonction des variations physiologiques du rythme cardiaque. Application à la cartograhie T2

Abstract : Cardiac Magnetic Resonance Imaging (MRI) requires to adapt the sequence to heart rate, so as to avoid the blur caused by the acquisition time longer than motion time constants. Thus, times between sequence radiofrequency pulses are as much variable as synchronization cardiac cycles durations. It causes imprecision on the resulting image, particularly for quantification. In fact, spins magnetization is not in a steady state during the acquisition. Two main research axis are presented in this thesis; the first one is a study of the impact of heart rate variation (described in the manuscript) on the transversal relaxation time T2 quantitative measurement. The study was lead on both phantom objects and on healthy volunteers. Two correction methods for heart rate variation are proposed, one based on the correction of the signal of the central line of the k-space, the other one based on a generalized reconstruction approach. First results are encouraging, and further works should be lead to confirm the methods efficacity. Then, heart rate variations are treated inside the cardiac cycle, and we propose a method to match the different segments of the electrocardiogram (ECG), based on the ECG deformation in the MR scanner probably due to by magnetohydrodynamic effect. This method is applied on imaging with a CINE kinetic sequence in which a better successive cardiac cycles segments matching should enable to improve image quality, at the condition to have sharp enough spatial and temporal resolutions. Results brought in this thesis are preliminary to necessary future researches in the sequence time domain, largely less addressed than organ motion
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Marion Soumoy de Roquefeuil. Adaptation des paramètres temporels en imagerie par résonance magnétique en fonction des variations physiologiques du rythme cardiaque. Application à la cartograhie T2. Autre. Université de Lorraine, 2013. Français. ⟨NNT : 2013LORR0080⟩. ⟨tel-01749843⟩

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