BRAIN CAST: An MRIQC-guided pipeline for age- and sex-specific pediatric brain MRI template construction, validated by downstream structural fidelity

Pediatric neuroimaging needs age- and sex-appropriate references, yet existing atlases span broad age ranges that blur development or lack sex specificity. We present BRAIN CAST: 28 year-by-year, sex-specific brain MRI templates covering ages 5-18, built from 1,272 quality-screened children in the Healthy Brain Network by an MRIQC-guided pipeline combining reduced-strength denoising, cerebrospinal-fluid-anchored intensity normalization, deep-learning skull stripping and iterative groupwise diffeomorphic registration. We evaluate templates not by image sharpness, which is not comparable across intensity conventions, but by the structural bias they induce downstream. Held-out children align to their matched template with sub-voxel gray-white interface error (1.1 mm); on a direction-symmetric surface-distance metric BRAIN CAST matches the best single-template reference and outperforms an age-specific pediatric atlas in 189 of 189 subjects. Female cortex is fit measurably better by female than by male templates, an effect no sex-neutral reference can provide. Templates, tissue-probability maps and the containerized pipeline are released.