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Practical considerations of diffusion-weighted MRS with ultra-strong diffusion gradients

Davies Jenkins, Christopher W., Döring, André, Fasano, Fabrizio, Kleban, Elena, Mueller, Lars, Evans, C. John, Afzali, Maryam, Jones, Derek K. ORCID:, Ronen, Itamar, Branzoli, Francesca and Tax, Chantal M. W. ORCID: 2023. Practical considerations of diffusion-weighted MRS with ultra-strong diffusion gradients. Frontiers in Neuroscience 17 , 1258408. 10.3389/fnins.2023.1258408

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Introduction: Diffusion-weighted magnetic resonance spectroscopy (DW-MRS) offers improved cellular specificity to microstructure—compared to water-based methods alone—but spatial resolution and SNR is severely reduced and slow-diffusing metabolites necessitate higher b-values to accurately characterize their diffusion properties. Ultra-strong gradients allow access to higher b-values per-unit time, higher SNR for a given b-value, and shorter diffusion times, but introduce additional challenges such as eddy-current artefacts, gradient non-uniformity, and mechanical vibrations. Methods: In this work, we present initial DW-MRS data acquired on a 3T Siemens Connectom scanner equipped with ultra-strong (300 mT/m) gradients. We explore the practical issues associated with this manner of acquisition, the steps that may be taken to mitigate their impact on the data, and the potential benefits of ultra-strong gradients for DW-MRS. An in-house DW-PRESS sequence and data processing pipeline were developed to mitigate the impact of these confounds. The interaction of TE, b-value, and maximum gradient amplitude was investigated using simulations and pilot data, whereby maximum gradient amplitude was restricted. Furthermore, two DW-MRS voxels in grey and white matter were acquired using ultra-strong gradients and high b-values. Results: Simulations suggest T2-based SNR gains that are experimentally confirmed. Ultra-strong gradient acquisitions exhibit similar artefact profiles to those of lower gradient amplitude, suggesting adequate performance of artefact mitigation strategies. Gradient field non-uniformity influenced ADC estimates by up to 4% when left uncorrected. ADC and Kurtosis estimates for tNAA, tCho, and tCr align with previously published literature. Discussion: In conclusion, we successfully implemented acquisition and data processing strategies for ultra-strong gradient DW-MRS and results indicate that confounding effects of the strong gradient system can be ameliorated, while achieving shorter diffusion times and improved metabolite SNR.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Physics and Astronomy
Cardiff University Brain Research Imaging Centre (CUBRIC)
Publisher: Frontiers Media
ISSN: 1662-453X
Funders: Wellcome Trust
Date of First Compliant Deposit: 14 December 2023
Date of Acceptance: 3 November 2023
Last Modified: 05 Jan 2024 06:18

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