Diffusion MRI tractography with along-tract profiling reveals subtle neurodevelopmental differences between moderate and late preterm infants

Abstract

PURPOSE: Moderately preterm (MP) infants (32-33 weeks' gestation) are at increased risk for developmental problems compared to late preterm (LP) infants (34-36 weeks' gestation). Fiber bundle tractography remains an unexplored avenue to understanding this risk-difference between MP and LP infants. This study aimed to examine along-tract profile differences between MP and LP infants at term-equivalent age (TEA). METHODS: Ninety-five infants (31 MP and 64 LP), born between November 2020 and March 2023, underwent MRI around TEA (40-44 weeks postmenstrual age). MRI included T2-weighted imaging and diffusion MRI (dMRI) with b-values 800 and 2000 s/mm2 (single shell). dMRI scans were preprocessed to reduce common artifacts. For all infants, 15 fiber bundles were reconstructed using TractSeg and along-tract profiles, expressed as fractional anisotropy (FA) and mean diffusivity (MD), and were compared between MP and LP infants using tractometry. RESULTS: Reconstructions with TractSeg demonstrated shape, position, and orientation of fiber bundles consistent with known neuroanatomy. FA and MD profiles were not significantly different between MP and LP infants. However, alternating trends towards along-tract profile differences between MP and LP infants were observed for multiple bundles. Wide 95% confidence intervals indicated substantial variability in fiber bundle organization within groups. CONCLUSION: Although not significant, along-tract differences between MP and LP infants suggest subtle alterations in white matter maturation. These findings indicate along-tract variability as potential focus for future research aimed at uncovering the mechanisms underlying early maturational differences and their potential role in later neurodevelopmental challenges encountered in moderate-late preterm infants.