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A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging

OBJECTIVE: We propose a framework to interpret the effects of High Permittivity Materials (HPM) on the performance of radiofrequency coils in Magnetic Resonance Imaging (MRI). METHODS: Based on a recent formulation of the scattering and propagation properties of spheres, we expanded the field in a l...

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Autores principales: Ruello, Giuseppe, Lattanzi, Riccardo
Formato: Online Artículo Texto
Lenguaje:English
Publicado: 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9724563/
https://www.ncbi.nlm.nih.gov/pubmed/35389860
http://dx.doi.org/10.1109/TBME.2022.3165763
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author Ruello, Giuseppe
Lattanzi, Riccardo
author_facet Ruello, Giuseppe
Lattanzi, Riccardo
author_sort Ruello, Giuseppe
collection PubMed
description OBJECTIVE: We propose a framework to interpret the effects of High Permittivity Materials (HPM) on the performance of radiofrequency coils in Magnetic Resonance Imaging (MRI). METHODS: Based on a recent formulation of the scattering and propagation properties of spheres, we expanded the field in a layered sphere as a superposition of ingoing and outgoing travelling waves, which allowed us to study the field components with a non-homogeneous transmission line model. We investigated the effects of a layer of HPM surrounding a head-mimicking uniform sphere at 7 tesla. RESULTS: Through the analysis of impedance and reflection coefficients, we show that by adjusting the properties of the HPM, it is possible to selectively amplify individual modes, or combination of them, modifying the overall field distribution in the sample and increasing signal-to-noise ratio at specific locations. Our results demonstrate that the observed enhanced MRI performance is not merely due to secondary fields generated by displacement currents in the HPM. CONCLUSIONS: Our formulation explains the effect of HPM in terms of matching, enabling the optimization of the electrical properties of the HPM with a simple mode-matching formula. SIGNIFICANCE: The proposed method could guide the design of novel radiofrequency coils with integrated HPM.
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spelling pubmed-97245632022-12-06 A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging Ruello, Giuseppe Lattanzi, Riccardo IEEE Trans Biomed Eng Article OBJECTIVE: We propose a framework to interpret the effects of High Permittivity Materials (HPM) on the performance of radiofrequency coils in Magnetic Resonance Imaging (MRI). METHODS: Based on a recent formulation of the scattering and propagation properties of spheres, we expanded the field in a layered sphere as a superposition of ingoing and outgoing travelling waves, which allowed us to study the field components with a non-homogeneous transmission line model. We investigated the effects of a layer of HPM surrounding a head-mimicking uniform sphere at 7 tesla. RESULTS: Through the analysis of impedance and reflection coefficients, we show that by adjusting the properties of the HPM, it is possible to selectively amplify individual modes, or combination of them, modifying the overall field distribution in the sample and increasing signal-to-noise ratio at specific locations. Our results demonstrate that the observed enhanced MRI performance is not merely due to secondary fields generated by displacement currents in the HPM. CONCLUSIONS: Our formulation explains the effect of HPM in terms of matching, enabling the optimization of the electrical properties of the HPM with a simple mode-matching formula. SIGNIFICANCE: The proposed method could guide the design of novel radiofrequency coils with integrated HPM. 2022-11 2022-10-19 /pmc/articles/PMC9724563/ /pubmed/35389860 http://dx.doi.org/10.1109/TBME.2022.3165763 Text en https://creativecommons.org/licenses/by/4.0/This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
spellingShingle Article
Ruello, Giuseppe
Lattanzi, Riccardo
A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging
title A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging
title_full A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging
title_fullStr A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging
title_full_unstemmed A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging
title_short A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging
title_sort physical framework to interpret the effects of high permittivity materials on radiofrequency coil performance in magnetic resonance imaging
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9724563/
https://www.ncbi.nlm.nih.gov/pubmed/35389860
http://dx.doi.org/10.1109/TBME.2022.3165763
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