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Non-invasive treatment of cardiac arrhythmias by high-intensity focussed ultrasound guided by magnetic resonance imaging

Abstract : High intensity focused ultrasound has the ability to deposit ultrasonic energy locally and non-invasively into biological tissues. It is possible to exploit the mechanical and/or thermal effects according to the ultrasonic parameters used. Guided by a Magnetic Resonance Imaging (MRI) scanner, this technology is equipped with a planning modality and real-time monitoring of the procedure. As of now, applications of MRI-guided focused ultrasound are on fixed organs, including brain and bone or uterine fibroid. For the heart, the presence of cardiac and respiratory movements constitutes an important difficulty, both for the ultrasonic (ballistic) treatment and for the temperature monitoring under MRI (artefacts on images). In addition, the rib cage acts as a barrier for the propagation of ultrasounds. In this thesis work, a set of new technological development have been developed for ablation and non-invasive cardiac stimulation using focused MRI-guided ultrasound. A first study shows the technical feasibility of controlling heart rhythm by short ultrasound pulses targeted to the myocardium. The influence of the parameters of the pulses (duration, amplitude, emission time in the cardiac cycle) were studied quantitatively on isolated beating heart then in vivo on a preclinical model. For this, an original device was developed. A second study presents new rapid MRI methods for simultaneously mapping the temperature and local displacement induced by focused ultrasound. The method is validated on the liver on a preclinical model and demonstrates that it is possible to correlate the thermal dose obtained by MR-thermometry with a change in the mechanical properties of the treated tissues measured simultaneously. A third study consisted in developing a technique for measuring the position of the target in 3D real-time using some elements of the ultrasonic transmitter as receivers. This measure allows to dynamically correct the position of the ultrasonic focus to maximize energy deposition at the targeted point. In addition, we monitored in real-time the procedure using MR-thermometry at a rate of 10 images per second. Here again a preclinical validation is presented. This thesis work proposes important advances to remove the current locks of the technology allowing to envision noninvasive treatments of cardiac pathologies, all guided by MRI in real-time.
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Submitted on : Thursday, December 20, 2018 - 11:07:38 AM
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  • HAL Id : tel-01961806, version 1

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Pierre Bour. Non-invasive treatment of cardiac arrhythmias by high-intensity focussed ultrasound guided by magnetic resonance imaging. Cardiology and cardiovascular system. Université de Bordeaux, 2017. English. ⟨NNT : 2017BORD0731⟩. ⟨tel-01961806⟩

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