Quantitative susceptibility mapping (QSM) may capture iron-sensitive cortical tissue susceptibility in Alzheimer’s disease (AD), but its relationship to amyloid-β (Aβ) topography remains unclear. We studied 697 memory-clinic participants with QSM, Aβ-PET and tau-PET across A/T-defined stages, including cognitively unimpaired controls, preclinical AD, MCI due to AD and AD dementia. Aβ burden was measured using global Centiloids and ROI-level cortical maps, while cortical QSM was summarized as voxel-weighted mean susceptibility across 68 Desikan-Killiany cortical ROIs. Aβ-PET increased broadly across the AD continuum, whereas cortical QSM elevations emerged with amyloid positivity but were spatially more restricted. Adjacent-stage ΔQSM showed weak and inconsistent spatial concordance with ΔAβ. These findings support cortical QSM as an amyloid-stage-relevant susceptibility marker, but not as a local amyloid PET surrogate.

Keywords: Alzheimer’s disease; QSM; quantitative susceptibility mapping; cortical iron; amyloid-β; Aβ-PET; Centiloid; tau-PET.