Normative T₁ and T₂ Brain Atlases Across the Adult Lifespan in a Chinese Cohort: Multicenter Quantitative MRI...

Quantitative MR relaxometry provides sensitive and reproducible measures of brain microstructure and is increasingly used in studies of ageing and neurodegenerative disease. However, normative brain atlases covering the adult lifespan remain scarce, especially from large, harmonized, multicenter datasets. This study aimed to establish lifespan-based normative T₁ and T₂ atlases to support individualized assessment and group-level comparisons. We retrospectively analyzed 947 healthy Han Chinese adults (421 males; median age 39 years; range 19-72) from 11 imaging centers in China. T₁ and T₂ maps were acquired with harmonized MP2RAGE and GRAPPATINI protocols, processed using a unified pipeline, and modeled with voxelwise mixed-effects regression including linear and quadratic age terms, sex, and random intercepts for site. Intersite reproducibility was further evaluated in three traveling subjects scanned at all centers. The atlases demonstrated region-specific age and sex effects in both white and gray matter. Intersite variability was minimal (intraclass correlation coefficients > 0.99 for T₁ and > 0.90 for T₂). Both T₁ and T₂ followed quadratic trajectories, decreasing in early adulthood, reaching minima in midlife, and increasing in later decades, with the strongest effects in cortical gray matter. Sex differences were most pronounced in parietal and callosal regions. These lifespan-based normative relaxometry atlases provide high-fidelity references for age- and sex-related microstructural changes in the healthy brain. They provide quantitative benchmarks for individualized profiling and group comparisons in Chinese adult populations, while validation in other ethnic populations remains necessary before broader application.