Paper detail

Associations between iron and mean kurtosis in iron-rich grey matter nuclei in aging

Elevated kurtosis values have been observed in subcortical grey matter structures of patients with neurodegenerative diseases. Here we tested whether these elevated values are related to iron content, which generate magnetic fields that add to the diffusion encoding gradients. Multi-shell diffusion and multi-echo gradient echo acquisitions were used to derive mean kurtosis and iron measures (R2* and magnetic susceptibility), respectively, in subcortical grey matter nuclei and white matter tracts in a discovery cohort (110 older and 63 younger adults) and replication cohort (72 healthy older adults). Iron-rich grey matter regions exhibited higher mean kurtosis, R2*, and magnetic susceptibility and white matter regions had lower mean kurtosis in the older adult group. In both cohorts, mean kurtosis was significantly correlated with R2* and magnetic susceptibility in iron-rich grey matter nuclei. No association was seen between signal-to-noise ratio and mean kurtosis in any grey matter region, indicating that the increase in mean kurtosis was not due to reduced signal-to-noise. Finally, a phantom experiment found higher mean kurtosis as iron concentrations increased. Our findings indicate that kurtosis is associated with iron-sensitive metrics in iron-rich grey matter structures, suggesting that kurtosis may be sensitive to iron deposits.