Shim coils tailored for correcting B0 inhomogeneity in the human brain (SCOTCH): Design methodology and 48-channel prototype assessment in 7-Tesla MRI

Meneses, Bruno Pinho; Stockmann, Jason P.; Arango, Nicolas; Gapais, Paul-François; Giacomini, Eric; Mauconduit, Franck; Gras, Vincent; Boulant, Nicolas; Vignaud, Alexandre; Luong, M.; Amadon, A.

doi:10.1016/j.neuroimage.2022.119498

Cited by 5 publications

(1 citation statement)

References 38 publications

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“…This arrangement is advantageous in accommodating variable subject positions and anatomical variations. However, the presence of coil redundancy is evident, prompting ongoing efforts to reduce this via dimensionality reduction methods such as Principal Component Analysis (PCA) analysis [ 44 ]. While an increased number of shim coils generally translates to enhanced shimming performance, our decision to utilize 51 coils sought to balance between robust shim with hardware simplicity.…”

Section: Discussionmentioning

confidence: 99%

Enhancing Whole-Brain Magnetic Field Homogeneity for 3D-Magnetic Resonance Spectroscopic Imaging with a Novel Unified Coil: A Preliminary Study

Malagi,

Li,

Zhang

et al. 2024

Cancers

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The spectral quality of magnetic resonance spectroscopic imaging (MRSI) can be affected by strong magnetic field inhomogeneities, posing a challenge for 3D-MRSI’s widespread clinical use with standard scanner-equipped 2nd-order shim coils. To overcome this, we designed an empirical unified shim–RF head coil (32-ch RF receive and 51-ch shim) for 3D-MRSI improvement. We compared its shimming performance and 3D-MRSI brain coverages against the standard scanner shim (2nd-order spherical harmonic (SH) shim coils) and integrated parallel reception, excitation, and shimming (iPRES) 32-ch AC/DC head coil. We also simulated a theoretical 3rd-, 4th-, and 5th-order SH shim as a benchmark to assess the UNIfied shim–RF coil (UNIC) improvements. In this preliminary study, the whole-brain coverage was simulated by using B0 field maps of twenty-four healthy human subjects (n = 24). Our results demonstrated that UNIC substantially improves brain field homogeneity, reducing whole-brain frequency standard deviations by 27% compared to the standard 2nd-order scanner shim and 17% compared to the iPRES shim. Moreover, UNIC enhances whole-brain coverage of 3D-MRSI by up to 34% compared to the standard 2nd-order scanner shim and up to 13% compared to the iPRES shim. UNIC markedly increases coverage in the prefrontal cortex by 147% and 47% and in the medial temporal lobe and temporal pole by 29% and 13%, respectively, at voxel resolutions of 1.4 cc and 0.09 cc for 3D-MRSI. Furthermore, UNIC effectively reduces variations in shim quality and brain coverage among different subjects compared to scanner shim and iPRES shim. Anticipated advancements in higher-order shimming (beyond 6th order) are expected via optimized designs using dimensionality reduction methods.

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Section: Discussionmentioning

confidence: 99%

Enhancing Whole-Brain Magnetic Field Homogeneity for 3D-Magnetic Resonance Spectroscopic Imaging with a Novel Unified Coil: A Preliminary Study

Malagi,

Li,

Zhang

et al. 2024

Cancers

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A 32‐channel high‐impedance honeycomb‐shaped receive array for temporal lobes exploration at 11.7T

Gapais,

Luong,

Giacomini

et al. 2024

Magnetic Resonance in Med

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PurposeThe newly operational 11.7T Iseult scanner provides an improved global SNR in the human brain. This gain in SNR can be pushed even further locally by designing region‐focused dense receive arrays. The temporal lobes are particularly interesting to neuroscientists as they are associated with language and concept recognition. Our main goal was to maximize the SNR in the temporal lobes and provide high‐acceleration capabilities for fMRI studies.MethodsWe designed and developed a 32‐channel receive array made of non‐overlapped hexagonal loops. The loops were arranged in a honeycomb pattern and targeted the temporal lobes. They were placed on a flexible neoprene cap closely fitting the head. A new stripline design with a high impedance was proposed and applied for the first time at 11.7T. Specific homebuilt miniaturized low‐impedance preamplifiers were directly mounted on the loops, providing preamplifier decoupling in a compact and modular design. Using an anatomical phantom, we experimentally compared the SNR and parallel imaging performance of the region‐focused cap to a 32‐channel whole‐brain receive array at 11.7T.ResultsThe experimental results showed a 1.7‐time higher SNR on average in the temporal lobes compared to the whole brain receive array. The g‐factor is also improved when undersampling in the antero‐posterior and head‐foot directions.ConclusionA significant SNR boost in the temporal lobes was demonstrated at 11.7T compared to the whole‐brain receive array. The parallel imaging capabilities were also improved in the temporal lobes in some acceleration directions.

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Germany’s journey toward 14 Tesla human magnetic resonance

Ladd

Quick

Speck

et al. 2023

Magn Reson Mater Phy

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Multiple sites within Germany operate human MRI systems with magnetic fields either at 7 Tesla or 9.4 Tesla. In 2013, these sites formed a network to facilitate and harmonize the research being conducted at the different sites and make this technology available to a larger community of researchers and clinicians not only within Germany, but also worldwide. The German Ultrahigh Field Imaging (GUFI) network has defined a strategic goal to establish a 14 Tesla whole-body human MRI system as a national research resource in Germany as the next progression in magnetic field strength. This paper summarizes the history of this initiative, the current status, the motivation for pursuing MR imaging and spectroscopy at such a high magnetic field strength, and the technical and funding challenges involved. It focuses on the scientific and science policy process from the perspective in Germany, and is not intended to be a comprehensive systematic review of the benefits and technical challenges of higher field strengths.

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Shim coils tailored for correcting B0 inhomogeneity in the human brain (SCOTCH): Design methodology and 48-channel prototype assessment in 7-Tesla MRI

Cited by 5 publications

References 38 publications

Enhancing Whole-Brain Magnetic Field Homogeneity for 3D-Magnetic Resonance Spectroscopic Imaging with a Novel Unified Coil: A Preliminary Study

Enhancing Whole-Brain Magnetic Field Homogeneity for 3D-Magnetic Resonance Spectroscopic Imaging with a Novel Unified Coil: A Preliminary Study

A 32‐channel high‐impedance honeycomb‐shaped receive array for temporal lobes exploration at 11.7T

Germany’s journey toward 14 Tesla human magnetic resonance

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