An Automated <scp>Analysis Tool</scp> for Diffusion Tensor Imaging‐Based Quantitative <scp>MRI</scp> in X‐Linked Adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is caused by ABCD1 pathogenic variants, leading to accumulation of very long-chain fatty acids (VLCFAs). Phenotypes include cerebral ALD (CALD) and adrenomyeloneuropathy (AMN). We assessed if quantitative MRI (qMRI) parameters from an automated tool (BrainQuant) could differentiate CALD from non-CALD and reflects myelopathy severity. Adult males from a prospective study (2015-2024) underwent annual neurological exams and brain MRI. Exclusion criteria were: fewer than two MRIs, non-ALD lesions, or prior transplantation. BrainQuant processed diffusion tensor imaging (DTI) to yield global metrics: fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). Patients were stratified by Loes score (0 vs. > 0) and expanded disability status scale (EDSS ≤ 2 vs. > 2). Longitudinal changes were modeled. Correlations with EDSS, severity score for progressive myelopathy (SSPROM), and 6-min walk test (6-MWT) were analyzed. The cohort included 62 patients (median age 36.5); 15 had CALD. Global DTI metrics did not differ significantly between CALD and non-CALD. A trend for higher radial diffusivity (RD) in the splenium (p = 0.037) was seen, but results were not significant after Bonferroni correction for multiple comparisons (p = 0.748). Patients with EDSS > 2 showed significantly worse global DTI values (p < 0.05), correlating with clinical scores (r = 0.40-0.69). Longitudinally, RD-global increased significantly (p < 0.001) at similar rates across EDSS groups. BrainQuant qMRI did not distinguish CALD and non-CALD but effectively tracked myelopathy. Radial diffusivity (RD)-global is a promising biomarker for monitoring X-ALD progression.