Repeatable tract-based diffusion metrics on a portable 64 mT MRI: a foundation for global population neuroscience

Royer, William, Gholam, James, Cercignani, Mara ORCID: https://orcid.org/0000-0002-4550-2456, Jones, Derek K. ORCID: https://orcid.org/0000-0003-4409-8049 and Kopanoglu, Emre ORCID: https://orcid.org/0000-0001-8982-4441 2026. Repeatable tract-based diffusion metrics on a portable 64 mT MRI: a foundation for global population neuroscience. Frontiers in Neuroimaging 5 , 1845201. 10.3389/fnimg.2026.1845201

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Abstract

Diffusion MRI underpins much of modern population neuroscience, yet scanner access remains concentrated in high-income settings, excluding the genetic, developmental, and disease diversity needed for generalizable discovery. Portable low-field MRI systems (field strengths below 0.1 T) offer a cheaper, infrastructure-light alternative that could extend diffusion imaging to under-represented populations, but only if the measurements are sufficiently repeatable. Here we provide the first systematic test-retest evaluation of tract-based diffusion tensor MRI (DT-MRI) metrics at 64 mT. Ten healthy participants were scanned at two time-points (median interval 13 days) with an 18-direction (b = 900s/mm2) diffusion protocol and a T2-weighted structural sequence on a portable 64 mT scanner. After correction for distortions and gradient imperfections, diffusion tensors were estimated and constrained spherical deconvolution was performed to enable bundle-specific tractography. Tract averaged fractional anisotropy, mean diffusivity, and radial diffusivity were extracted from a selection of white-matter tracts spanning projection, association, and commissural fiber categories. Bland-Altman analysis and within-subject coefficients of variation indicated strong scan-rescan agreement, while intraclass correlation coefficients were variable across tracts and metrics. Compared with high-field data, coefficients of variation were 3–10 times larger and standard deviations in the means were approximately an order of magnitude higher. Despite this, statistical power calculations yielded feasible sample-size estimates for detecting group differences in a two-tailed t-test: for a 4% difference in means, approximately 25 participants per group were sufficient for the majority of tracts in MD and RD, and around 65 for FA. Although absolute DT-MRI metric values diverge from high-field references due to partial volume effects and noise-floor bias, continued advances in acquisition, reconstruction, and processing are expected to further narrow this gap. The results demonstrate that portable 64 mT MRI can deliver repeatable DT-MRI metrics, establishing a foundation for democratizing advanced neuroimaging and enabling population-scale studies in regions that have historically been excluded from brain research.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Psychology Research Institutes & Centres > Cardiff University Brain Research Imaging Centre (CUBRIC)
Publisher:	Frontiers Media
ISSN:	2813-1193
Funders:	Wellcome Trust
Projects:	317797/Z/24/Z, 227882/Z/23/Z
Date of First Compliant Deposit:	6 August 2026
Date of Acceptance:	9 July 2026
Last Modified:	30 Sep 2026 10:18
URI:	https://orca.cardiff.ac.uk/id/eprint/188765

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