Assessing Age-Associated Influences on Paramagnetic and Diamagnetic Susceptibility Maps in Postmortem Human Brains.

Diamagnetic susceptibility showed a consistent age-related decline in deep gray matter basal ganglia regions.

• The study used APART-QSM method for susceptibility separation applied to in situ postmortem MRI data from 47 subjects aged 31–91 years.
• Linear regression was used to assess age-related associations with susceptibility values in 17 deep gray matter (DGM) and white matter (WM) regions.
• The age-related decline in diamagnetic susceptibility across DGM basal ganglia regions appeared to result from a shared underlying factor across these areas.

A negative correlation was found between fractional anisotropy (FA) and diamagnetic susceptibility in white matter regions, suggesting a potential myelin contribution to the diamagnetic component.

• FA was used as a proxy measure reflecting myelin integrity in white matter regions.
• The negative correlation between FA and diamagnetic susceptibility was interpreted as indicating a myelin contribution to the diamagnetic susceptibility component.
• This analysis was conducted across white matter regions included in the 17 DGM and WM regions examined.

The putamen was the only region in which paramagnetic and total QSM susceptibility values increased linearly with age.

• Paramagnetic, diamagnetic, and total QSM susceptibility were assessed across 17 deep gray matter and white matter regions.
• The putamen showed a strong age association for both paramagnetic and total QSM susceptibility values in the postmortem condition.
• Results were consistent with previously reported in vivo analyses, supporting cross-validation between postmortem and in vivo conditions.
• The putamen was uniquely identified as the only region showing a linear increase in susceptibility values with age.

Ex vivo putamen tissue analysis revealed a moderate association between paramagnetic susceptibility and iron concentration.

• Tissue samples from ex vivo putamen were analyzed for iron concentration and compared with MRI-derived paramagnetic susceptibility maps.
• The association was described as 'moderate,' supporting iron's biological contribution to MRI paramagnetic susceptibility maps of the putamen.
• This finding promotes cross-validation between imaging and direct tissue analysis.

Postmortem in situ MRI using APART-QSM was applied to 47 subjects to investigate age-related changes in susceptibility components.

• The sample consisted of 47 subjects with ages ranging from 31 to 91 years.
• MRI data were acquired in situ (intracranial) in a postmortem setting.
• The APART-QSM method was used to separate paramagnetic and diamagnetic components of magnetic susceptibility.
• Seventeen deep gray matter and white matter regions were analyzed.
• Results were compared with previously reported in vivo age associations to assess biological validity.