Association between AI-based whole-brain volume measurements and radiology report–based atrophy grades

Abstract

Background: The Global Cortical Atrophy (GCA) scale is widely used for visual assessment of cortical atrophy on MRI but is subject to interobserver variability. Automated brain volumetry provides objective measurements; however, its association with visual atrophy grading remains understudied in Mongolia. Aim: To assess the association and agreement between radiology report–based atrophy grades and AI-derived wholebrain volume, and to compare brain volumes in adults with and without type 2 diabetes mellitus (T2DM). Materials and Methods: This retrospective, single-center study included 367 adults aged ≥40 years (T2DM, n=144; controls, n=223). Intracranial volume–adjusted whole-brain volumes were obtained from 3D T1-weighted MRI using Neurophet AQUA v3.1. Atrophy severity recorded in routine radiology reports was coded from 0 to 3. Welch’s ANOVA assessed differences across grades, and ROC analysis evaluated discrimination between adjacent grades. Classification agreement was assessed using stratified five-fold cross-validation and Cohen’s κ. Ageand sex-adjusted ANCOVA compared brain volumes between groups. Results: Mean whole-brain volume decreased across atrophy grades 0–3 (1122.12, 1068.50, 1034.76, and 968.33 mL; Welch’s F(3, 60.04)=207.30; P<0.001). ROC AUCs for adjacent grades were 0.892, 0.897, and 1.000, with corresponding thresholds of 1099.86, 1056.17, and 995.57 mL. Five-fold cross-validation yielded 78.7% exact agreement (289/367), unweighted κ=0.684, and quadratic-weighted κ=0.856. Adjusted whole-brain volume was 11.98 mL lower in T2DM than in controls (95% CI, −22.67 to −1.30; P=0.028), whereas the overall association between T2DM and atrophy grade was not statistically significant (P=0.059). Conclusion: Higher report-based atrophy grades were associated with lower whole-brain volumes, with strong quadraticweighted agreement between volumetric and report-based classifications. Adults with T2DM had lower adjusted brain volumes than controls. Automated volumetry may complement radiologists’ assessments by providing objective quantitative information.