Abstract Intraoperative surgery has created a need to develop new kinds of surgical tools. Also, the development of imaging techniques and devices has precipitated the need. Robotics plays an increasingly important role in surgery. A robot can yield better accuracy, smaller movements and, as a result, a faster healing process than a normal operation would require for recovering and healing larger cuts in the human body. Magnetic resonance imaging, MRI, is one of the safest imaging techniques, and it has excellent soft tissue contrast. In the last few years, MRI has become a more frequently-used technique in the intraoperative surgery, such as the biopsy. Brain biopsies in particular are easier to perform by the help of MRI. When designing a robot, or any other mechatronic device, for an MR environment, it becomes vital to consider its appropriateness, i.e., electric and magnetic compatibility with MRI. The latter is a notion related to the surgical procedure and the magnetic field being applied. It implies that instrumentation has to be more compatible with MR in higher magnetic fields. In this study, an MR-compatible robot was developed to work inside open MRI equipment. The MR compatibility of the robot was evaluated, using the testing method evolved during the study. The method helps select the suitable material and parts for mechatronic devices operating under MRI. Most notably, this work also devised and introduced new types of sensors to achieve better MR compatibility of the equipment. As a result of this research, a suitable material was developed for the robot's body as well as for the sensors, actuators and tools. Furthermore, it was deduced that some sensors and the control system when powered can not be used in the MR scanner at all. A further result was that the movement of a robotic arm does not disturb image quality in any way. The testing method developed in this research helps address the compatibility issues arising from the use of any device that works in MRI. The testing method can be used for magnetic fields of different strengths. The robot and the control parts constructed in the research were tested under a 0.23-T open MRI scanner. The results show which materials and fibre optics provide a highly MR compatible solution for an MRI environment. The results also show that normal electric motors can not be driven close to the magnetic field while imaging.

This thesis presents technical and methodological developments aiming tooffer a viable alternative for the treatment of digestive cancers (rectum and esophagus). Compared to the standard methods of therapy, the high intensity contact ultrasound guided by MRI is a less invasive approach. MRI offers 2 advantages: good spatial resolution, and real-time temperature control. This treatment method requires efficacy and safety. Three prototypes of RF coil integrated with ultrasound transducers were built in order to increase the spatial and temporal resolution ofthe MR images, and the accuracy of the temperature measurement. The integrated coils showed a better sensitivity compared to a standard extracorporeal coil. Anatomical (voxel 0.4x0.4x5 mm3)and thermometry (voxel 0.75x0.75x8 mm3, 2s/image) high resolution MR images were acquired in-vivo. The temperature was measured, within a radius of 20 mm from the balloon, with a standard deviation <1°C. The flow artifacts caused by the water circulating inside the cooling balloon could be shifted out of the region of interest. The temperature evolution was controlled automatically, at different depths, with one control point per beam. The controller showed a good accuracy during in-vivo experiments (standard deviation less than 5%). The phased-arrayultra sound transducer permits the successive activation of multiple beams during the same dynamic of sonication. Simulations were conducted in order to offer an optimal treatment planning for a defined tumor. A new design of ultrasound transducer with 256 elements with revolution symmetry, based on a natural geometrical focalization, was proposed.

Cette thèse présente des développements techniques et méthodologiques visant une alternative viable pour le traitement des cancers digestifs (rectum, œsophage). Par rapport aux méthodes standards de thérapie, les ultrasons de contact de haute intensité sous guidage IRM sont une approche moins invasive. L’IRM offre 2 avantages: bonne résolution spatiale et contrôle en temps réel de la température. Cette méthode de traitement demande efficacité et sécurité. Trois prototypes d’antenne RF intégrées à des transducteurs ultrasonores ont été réalisés afin d’améliorer la résolution spatiale et temporelle des images IRM et la précision de la mesure de température. Les antennes intégrées ont montré une meilleure sensibilité par rapport à une antenne extra corporelle standard. Des images IRM haute résolution, anatomiques (voxel0.4x0.4x5 mm3) et de thermométrie (voxel 0.75x0.75x8 mm3, 2s/image) ont été acquises in-vivo.La température a été mesurée, dans un rayon de 20 mm au-delà du ballon, avec un écart type<1°C. Les artéfacts de flux causés par l’eau circulante à l’intérieur du ballon de refroidissement ont pu être projetés hors de la région d’intérêt. L’évolution de la température a été contrôlée automatiquement, à des profondeurs variables, avec un point de contrôle par faisceau. Le contrôleur a montré une grande précision in-vivo (écart type <5%). Le transducteur ultrasonore matriciel permet d’activer successivement plusieurs faisceaux pendant la même dynamique de tir.Des simulations ont été conduites afin de proposer une planification du traitement optimale pour une tumeur désignée. Un nouveau concept de sonde ultrasonore à 256 éléments avec focalisation géométrique naturelle a été proposé. / This thesis presents technical and methodological developments aiming tooffer a viable alternative for the treatment of digestive cancers (rectum and esophagus). Compared to the standard methods of therapy, the high intensity contact ultrasound guided by MRI is a less invasive approach. MRI offers 2 advantages: good spatial resolution, and real-time temperature control. This treatment method requires efficacy and safety. Three prototypes of RF coil integrated with ultrasound transducers were built in order to increase the spatial and temporal resolution ofthe MR images, and the accuracy of the temperature measurement. The integrated coils showed a better sensitivity compared to a standard extracorporeal coil. Anatomical (voxel 0.4x0.4x5 mm3)and thermometry (voxel 0.75x0.75x8 mm3, 2s/image) high resolution MR images were acquired in-vivo. The temperature was measured, within a radius of 20 mm from the balloon, with a standard deviation <1°C. The flow artifacts caused by the water circulating inside the cooling balloon could be shifted out of the region of interest. The temperature evolution was controlled automatically, at different depths, with one control point per beam. The controller showed a good accuracy during in-vivo experiments (standard deviation less than 5%). The phased-arrayultra sound transducer permits the successive activation of multiple beams during the same dynamic of sonication. Simulations were conducted in order to offer an optimal treatment planning for a defined tumor. A new design of ultrasound transducer with 256 elements with revolution symmetry, based on a natural geometrical focalization, was proposed.

In recent years, development of various imaging, recording and stimulation tools are rapidly advancing our knowledge of the human anatomy and its underlying interconnections. As a truly non-invasive tool, Magnetic Resonance Imaging (MRI), is creating new opportunities to understand large scale biological processes with a fine detail. Furthermore, novel materials and microfabrication techniques are allowing researchers to develop tools that record bio-signal or modulate complex physiology with high temporal precision. However, these tools, when used individually can elucidate only a partial view of the human body and the brain. There is a growing need in both the research and clinical community to find ways to perform these modalities together and visualize biological systems across a vast range of spatiotemporal scale. However, severe methodological challenges act as bottlenecks for any such multimodal integration.<br><div><br></div><div>To address this critical need, I have designed an MRI-safe platform for high-fidelity bio-signal recording and electrical stimulation during concurrent MRI imaging. Central to this system are novel miniaturized microelectronic devices, that operate wirelessly in synchrony with MRI scans. The system leverages surplus functionalities of a conventional scanner to integrate with the imaging system and provide a simple and inexpensive solution towards multimodal imaging. This work also describes a systematic approach for development and evaluation of this plug-and-play system through in-vivo experiments in animal models. The clinical relevance of the multimodal imaging platform was further showcased through a study on the mechanism of SUDEP (Sudden death in epilepsy), a terminal complication associated with epilepsy. With future refinements, I expect this platform will provide affordable, accessible, and reliable solutions for multimodal imaging in animals and humans, creating unique opportunities for basic scientific research and clinical diagnosis.<br></div>