Age-related changes in the healthy adult visual pathway: evidence from diffusion tensor imaging with fixel-based analysis

Background and purposeFixel-based analysis (FBA) is a new method that overcomes the technical limitations of diffusion tensor imaging (DTI) by enabling the characterization of multiple fiber populations within a voxel, and provides biologically meaningful indicators. This study aimed to explore age-related changes in the visual pathway in healthy adults and to observe differences in imaging quality between data collected using different b‑values.MethodsIn this prospective cross-sectional study, brain DTI scans which were collected with more than six uniformly distributed gradient directions and higher b‑values (up to 2000 s/mm2) than traditional DTI were performed in 72 healthy adults across the adult lifespan (20–79 years). After image preprocessing, FBA was used to process the dataset. At the same time, conventional DTI metrics were also calculated.ResultsPearson’s correlation analysis showed that DTI parameters of white matter (optic nerve, optic chiasma, optic tract, and optic radiation) in the optic pathway were correlated with age. FA values were negatively correlated with age, while MD/AD/RD showed a positive correlation (P