AUTHOR=Davies-Jenkins Christopher W. , Döring André , Fasano Fabrizio , Kleban Elena , Mueller Lars , Evans C. John , Afzali Maryam , Jones Derek K. , Ronen Itamar , Branzoli Francesca , Tax Chantal M. W. 

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

JOURNAL=Frontiers in Neuroscience

VOLUME=17

YEAR=2023

URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2023.1258408

DOI=10.3389/fnins.2023.1258408

ISSN=1662-453X

ABSTRACT=<sec><title>Introduction</title><p>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 <italic>b</italic>-values to accurately characterize their diffusion properties. Ultra-strong gradients allow access to higher <italic>b</italic>-values per-unit time, higher SNR for a given <italic>b</italic>-value, and shorter diffusion times, but introduce additional challenges such as eddy-current artefacts, gradient non-uniformity, and mechanical vibrations.</p></sec><sec><title>Methods</title><p>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, <italic>b</italic>-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 <italic>b</italic>-values.</p></sec><sec><title>Results</title><p>Simulations suggest T<sub>2</sub>-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.</p></sec><sec><title>Discussion</title><p>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.</p></sec>