ArticleMagnetic resonance in medicine2019
Disentangling the effects of high permittivity materials on signal optimization and sample noise reduction via ideal current patterns.
Article in Magnetic resonance in medicine, 2019. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 6 papers.
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Who cites it
6 citing papers in PubMed.
- A theoretical framework to investigate the effect of high permittivity materials in MRI using anatomy-mimicking cylinders.Magnetic resonance in medicine · 2024Article
- Computational methods for the estimation of ideal current patterns in realistic human models.Magnetic resonance in medicine · 2024Article
- Novel materials in magnetic resonance imaging: high permittivity ceramics, metamaterials, metasurfaces and artificial dielectrics.Magma (New York, N.Y.) · 2022Review
- A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging.IEEE transactions on bio-medical engineering · 2022Article
- Neuroimaging at 7 Tesla: a pictorial narrative review.Quantitative imaging in medicine and surgery · 2022Review
- Scattering from Spheres: A New Look into an Old Problem.Electronics · 2021Article
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Authors and funding
4 authors.
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Abstract
purposeTo investigate how high-permittivity materials (HPMs) can improve SNR when placed between MR detectors and the imaged body.
methodsWe used a simulation framework based on dyadic Green's functions to calculate the electromagnetic field inside a uniform dielectric sphere at 7 Tesla, with and without a surrounding layer of HPM. SNR-optimizing (ideal) current patterns were expressed as the sum of signal-optimizing (signal-only) current patterns and dark mode current patterns that minimize sample noise while contributing nothing to signal. We investigated how HPM affects the shape and amplitude of these current patterns, sample noise, and array SNR.
resultsIdeal and signal-only current patterns were identical for a central voxel. HPMs introduced a phase shift into these patterns, compensating for signal propagation delay in the HPMs. For an intermediate location within the sphere, dark mode current patterns were present and illustrated the mechanisms by which HPMs can reduce sample noise. High-amplitude signal-only current patterns were observed for HPM configurations that shield the electromagnetic field from the sample. For coil arrays, these configurations corresponded to poor SNR in deep regions but resulted in large SNR gains near the surface due to enhanced fields in the vicinity of the HPM. For very high relative permittivity values, HPM thicknesses corresponding to even multiples of λ/4 resulted in coil SNR gains throughout the sample.
conclusionHPMs affect both signal sensitivity and sample noise. Lower amplitude signal-only optimal currents corresponded to higher array SNR performance and could guide the design of coils integrated with HPM.
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