Lipid suppression for brain MRI and MRSI by means of a dedicated crusher coil

Boer, Vincent O.; Lindt, T. Van de; Luijten, Peter R.; Klomp, Dennis W. J.

doi:10.1002/mrm.25331

Cited by 43 publications

(50 citation statements)

References 34 publications

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“…Thus, our results show that neither extracranial lipids nor MM contributions significantly reduced reproducibility compared to other reports, although both are enhanced in FID‐MRSI, especially when highly accelerated by parallel imaging. A further reduction of lipid artifacts via dedicated lipid removal hardware or spatial‐spectral encoding is expected to further improve the reproducibility.…”

Section: Discussionmentioning

confidence: 99%

Effects of different macromolecular models on reproducibility of FID‐MRSI at 7T

Hečková

Považan²,

Strasser

et al. 2019

Magnetic Resonance in Med

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Purpose A properly characterized macromolecular (MM) contribution is essential for accurate metabolite quantification in FID‐MRSI. MM information can be included into the fitting model as a single component or parameterized and included over several individual MM resonances, which adds flexibility when pathologic changes are present but is prone to potential overfitting. This study investigates the effects of different MM models on MRSI reproducibility. Methods Clinically feasible, high‐resolution FID‐MRSI data were collected in ~5 min at 7 Tesla from 10 healthy volunteers and quantified via LCModel (version 6.3) with 3 basis sets, each with a different approach for how the MM signal was handled: averaged measured whole spectrum (full MM), 9 parameterized components (param MM) with soft constraints to avoid overparameterization, or without any MM information included in the fitting prior knowledge. The test–retest reproducibility of MRSI scans was assessed voxel‐wise using metabolite coefficients of variation and intraclass correlation coefficients and compared between the basis sets. Correlations of concentration estimates were investigated for the param MM fitting model. Results The full MM model provided the most reproducible quantification of total NAA, total Cho, myo‐inositol, and glutamate + glutamine ratios to total Cr (coefficients of variations ≤ 8%, intraclass correlation coefficients ≥ 0.76). Using the param MM model resulted in slightly lower reproducibility (up to +3% higher coefficients of variations, up to −0.1 decreased intraclass correlation coefficients). The quantification of the parameterized macromolecules did not affect quantification of the overlapping metabolites. Conclusion Clinically feasible FID‐MRSI with an experimentally acquired MM spectrum included in prior knowledge provides highly reproducible quantification for the most common neurometabolites in healthy volunteers. Parameterization of the MM spectrum may be preferred as a compromise between quantification accuracy and reproducibility when the MM content is expected to be pathologically altered.

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Section: Discussionmentioning

confidence: 99%

Effects of different macromolecular models on reproducibility of FID‐MRSI at 7T

Hečková

Považan²,

Strasser

et al. 2019

Magnetic Resonance in Med

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“…A large volume was carefully shimmed to prevent the subcutaneous lipids from resonating within the metabolite chemical shift range and a lipid decontamination was used in postprocessing, based on an L2‐norm‐regularized reconstruction proposed by Bilgic et al . Other solutions will be considered in future studies, such as dedicated gradient crusher coils , higher order shims , constrained shimming routines , outer volume saturation , and (double) inversion recovery methods .…”

Section: Discussionmentioning

confidence: 99%

(2 + 1)D-CAIPIRINHA accelerated MR spectroscopic imaging of the brain at 7T

et al. 2016

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PurposeTo compare a new parallel imaging (PI) method for multislice proton magnetic resonance spectroscopic imaging (1H‐MRSI), termed (2 + 1)D‐CAIPIRINHA, with two standard PI methods: 2D‐GRAPPA and 2D‐CAIPIRINHA at 7 Tesla (T).Methods(2 + 1)D‐CAIPIRINHA is a combination of 2D‐CAIPIRINHA and slice‐CAIPIRINHA. Eight healthy volunteers were measured on a 7T MR scanner using a 32‐channel head coil. The best undersampling patterns were estimated for all three PI methods. The artifact powers, g‐factors, Cramér–Rao lower bounds (CRLB), and root mean square errors (RMSE) were compared quantitatively among the three PI methods. Metabolic maps and spectra were compared qualitatively.Results(2 + 1)D‐CAIPIRINHA allows acceleration in three spatial dimensions in contrast to 2D‐GRAPPA and 2D‐CAIPIRINHA. Thus, this sequence significantly decreased the RMSE of the metabolic maps by 12.1 and 6.9%, on average, for 4 < R < 11, compared with 2D‐GRAPPA and 2D‐CAIPIRINHA, respectively. The artifact power was 22.6 and 8.4% lower, and the CRLB were 3.4 and 0.6% lower, respectively.Conclusion(2 + 1)‐CAIPIRINHA can be implemented for multislice MRSI in the brain, enabling higher accelerations than possible with two‐dimensional (2D) parallel imaging methods. An eight‐fold acceleration was still feasible in vivo with negligible PI artifacts with lipid decontamination, thus decreasing the measurement time from 120 to 15 min for a 64 × 64 × 4 matrix. Magn Reson Med 78:429–440, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

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“…Both, increased spatial resolution and spectral bandwidth, lead to increased demands on gradient systems and ultimately lower signal‐to‐noise ratio (SNR) efficiency 16, 17. Parallel imaging, on the other hand, becomes more efficient at higher B 0 , but achievable accelerations are lower than for SSE (

\leq 10

) 15 and lipid contamination is aggravated, which calls for additional lipid suppression techniques 2, 18, 19. While established SSE trajectories (i.e., EPSI, spirals) can be certainly optimized for higher B 0 , the increased gradient demands at 7T due to the increased spectral bandwidth make these trajectories inefficient for high spatial resolutions.…”

Section: Introductionmentioning

confidence: 99%

Density‐weighted concentric circle trajectories for high resolution brain magnetic resonance spectroscopic imaging at 7T

Hingerl

Bogner

Moser

et al. 2017

Magnetic Resonance in Med

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PurposeFull‐slice magnetic resonance spectroscopic imaging at ≥7 T is especially vulnerable to lipid contaminations arising from regions close to the skull. This contamination can be mitigated by improving the point spread function via higher spatial resolution sampling and k‐space filtering, but this prolongs scan times and reduces the signal‐to‐noise ratio (SNR) efficiency. Currently applied parallel imaging methods accelerate magnetic resonance spectroscopic imaging scans at 7T, but increase lipid artifacts and lower SNR‐efficiency further. In this study, we propose an SNR‐efficient spatial‐spectral sampling scheme using concentric circle echo planar trajectories (CONCEPT), which was adapted to intrinsically acquire a Hamming‐weighted k‐space, thus termed density‐weighted‐CONCEPT. This minimizes voxel bleeding, while preserving an optimal SNR.Theory and MethodsTrajectories were theoretically derived and verified in phantoms as well as in the human brain via measurements of five volunteers (single‐slice, field‐of‐view 220 × 220 mm2, matrix 64 × 64, scan time 6 min) with free induction decay magnetic resonance spectroscopic imaging. Density‐weighted‐CONCEPT was compared to (a) the originally proposed CONCEPT with equidistant circles (here termed e‐CONCEPT), (b) elliptical phase‐encoding, and (c) 5‐fold Controlled Aliasing In Parallel Imaging Results IN Higher Acceleration accelerated elliptical phase‐encoding.ResultsBy intrinsically sampling a Hamming‐weighted k‐space, density‐weighted‐CONCEPT removed Gibbs‐ringing artifacts and had in vivo +9.5%, +24.4%, and +39.7% higher SNR than e‐CONCEPT, elliptical phase‐encoding, and the Controlled Aliasing In Parallel Imaging Results IN Higher Acceleration accelerated elliptical phase‐encoding (all P < 0.05), respectively, which lead to improved metabolic maps.ConclusionDensity‐weighted‐CONCEPT provides clinically attractive full‐slice high‐resolution magnetic resonance spectroscopic imaging with optimal SNR at 7T. Magn Reson Med 79:2874–2885, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Lipid suppression for brain MRI and MRSI by means of a dedicated crusher coil

Abstract: Outer volume crushing allows for simple fat suppression and boosts scanning efficiency, which is particularly beneficial at ultra-high field strengths.

Cited by 43 publications

References 34 publications

Effects of different macromolecular models on reproducibility of FID‐MRSI at 7T

Effects of different macromolecular models on reproducibility of FID‐MRSI at 7T

(2 + 1)D-CAIPIRINHA accelerated MR spectroscopic imaging of the brain at 7T

Density‐weighted concentric circle trajectories for high resolution brain magnetic resonance spectroscopic imaging at 7T

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