Metamaterial antennas for medical imaging

Details

Supervisors

Craeye, Christophe

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil électricien, à finalité spécialisée

Abstract

Nuclei’s magnetic properties are the basis for Nuclear Magnetic Resonance (NMR). The properties of subatomic particles are determined by quantum physics. The medical use of NMR is referred to as Magnetic Resonance Imaging (MRI). Innovations such as this have proven to be essential and extremely useful in the medical field. When applying NMR, RF coils are needed. The choice of these RF coils and their design is essential if a quality image is expected. In the case of Birdcages, volume coils are generally used as transceiver coils. However, surface coils have been used as receiver coils, especially at UHF MRI. Over the past 30 years, since the invention of the birdcage, the literature shows a huge number of variants of the basic model known as the conventional birdcage. These variants were designed to solve specific problems. There are however several issues that could be solved going back to the conventional birdcage: (i) The non-central location of the region of interest (ROI) (ii) The increase in homogeneity in this ROI. To this day, little literature provides numerical and experimental data on these subjects. The medical world has stated its interest, and therefore this thesis aims to provide more insights into the possibilities offered by the birdcage. In order to define the ROI and the desired field, Gaussian distributed weight matrices are used. Therefore, different versions of Gaussians as well as their specific definition are presented. To the authors’ knowledge, such analysis has never been proposed before. A Method of Moments (MoM) based numerical simulation code is adapted to incorporate and take into account the weight matrix. Its main goal is to simulate and optimize the components value of the Birdcage in order to increase the homogeneity in the ROI. Based on the results, a more complex and concrete medical application of the approach, Functional imaging, is presented. The interest not only in the homogeneity but also in the shape of the fields leads to the introduction of a new metric and possibilities.