This article reviews recent developments in designing and testing new types of materials which can be: (i) placed around the body for in vivo imaging, (ii) be integrated into a conventional RF coil... Show moreThis article reviews recent developments in designing and testing new types of materials which can be: (i) placed around the body for in vivo imaging, (ii) be integrated into a conventional RF coil, or (iii) form the resonator itself. These materials can improve the quality of MRI scans for both in vivo and magnetic resonance microscopy applications. The methodological section covers the basic operation and design of two different types of materials, namely high permittivity materials constructed from ceramics and artificial dielectrics/metasurfaces formed by coupled conductive subunits, either in air or surrounded by dielectric material. Applications of high permittivity materials and metasurfaces placed next to the body to neuroimaging and extremity imaging at 7 T, body and neuroimaging at 3 T, and extremity imaging at 1.5 T are shown. Results using ceramic resonators for both high field in vivo imaging and magnetic resonance microscopy are also shown. The development of new materials to improve MR image quality remains an active area of research, but has not yet found significant use in clinical applications. This is mainly due to practical issues such as specific absorption rate modelling, accurate and reproducible placement, and acceptable size/weight of such materials. The most successful area has been simple "dielectric pads" for neuroimaging at 7 T which were initially developed somewhat as a stop-gap while parallel transmit technology was being developed, but have continued to be used at many sites. Some of these issues can potentially be overcome using much lighter metasurfaces and artificial dielectrics, which are just beginning to be assessed. Show less
Moussu, M.A.C.; Abdeddaim, R.; Dubois, M.; Georget, E.; Webb, A.G.; Nenasheva, E.; ... ; Enoch, S. 2022
Comments about the above article [1] were proposed. We thank and reply to the authors of the comments about our model of high-permittivity dielectric ring resonators used as microscopy magnetic... Show moreComments about the above article [1] were proposed. We thank and reply to the authors of the comments about our model of high-permittivity dielectric ring resonators used as microscopy magnetic resonance probes. In this prospect, we reply part by part to the comments. Show less
Moussu, M.A.C.; Abdeddaim, R.; Dubois, M.; Georget, E.; Webb, A.G.; Nenasheva, E.; ... ; Enoch, S. 2020
Magnetic resonance imaging (MRI) is an imaging technique exploiting the magnetic resonance (MR) of specific nuclear spins, like protons. In this article, MR probes based on dielectric ring... Show moreMagnetic resonance imaging (MRI) is an imaging technique exploiting the magnetic resonance (MR) of specific nuclear spins, like protons. In this article, MR probes based on dielectric ring resonators are investigated from a theoretical approach. We take advantage of the high-permittivity and low-loss properties of the ceramic material used for manufacturing these probes for microscopy applications. Magnetic resonance microscopy (MRM) aims at imaging tiny samples with a sufficient resolution to distinguish small details. In this framework, compact resonators, called volume probes, contain the investigated sample and are used for both signal transmission and reception. The newly developed semi-analytical model enables the estimation of the frequency of the first transverse electric mode of a cylindrical resonator. It also provides a method to compute the corresponding magnetic field distribution, the dielectric losses contributions from the probe and the sample, and the signal-to-noise ratio (SNR). The proposed approach aims at providing design guidelines for dielectric probes. Show less
