Susceptibility source separation unveils iron and myelin trajectories in healthy brain development and aging

Motivation: Iron and myelin changes in the human brain have not been studied independently in a large cohort that includes children. Goal(s): Evaluate how paramagnetic (iron) and diamagnetic (myelin) susceptibilities change in human brain across the lifespan. Approach: Susceptibility source separation was performed on 339 healthy controls (5-90 years, 194 females) with age trajectories assessed in deep gray matter and white matter. Results: Iron-rich deep gray matter regions had an increase in both paramagnetic and diamagnetic susceptibility across the lifespan. In white matter regions, both sources increased at early ages and decreased with aging after a peak (~50-60). Impact: Paramagnetic and diamagnetic maps unveiled independent iron and myelin trajectories in development and aging, removing confounds found in total susceptibility.