Characterizing iron deposits in subcortical grey matter from in vivo gradient-echo data

Motivation: Transverse relaxation rate and magnetic susceptibility are MRI measures of iron concentration in subcortical grey matter. However, their relation to the microscopic distribution of iron deposits within the tissue remains elusive. Goal(s): Our goal is to characterize the distribution of iron deposits in subcortical grey matter from in vivo gradient-echo data. Approach: We characterize iron-rich deposits from the combination of transverse relaxation parameters of the magnitude and phase of gradient-echo data, under two limiting regimes. Results: The estimates of iron distribution are consistent with ex vivo studies. Data suggest that an intermediate regime might be applicable in subcortical tissue. Impact: The characterization of the microscopic distribution of iron deposits in subcortical grey matter, from in vivo gradient-echo data, brings the opportunity to study iron-related brain changes in neurodegenerative diseases with improved specificity.