Iron Content in Deep Gray Matter as a Function of Age Using Quantitative Susceptibility Mapping: A Multicenter Study

Area of Science:

• Neuroimaging
• Biomarkers
• Quantitative Susceptibility Mapping

Background:

• Iron accumulation in the deep gray matter (DGM) is linked to aging and neurodegenerative diseases.
• Quantitative susceptibility mapping (QSM) is a promising MRI technique for non-invasively assessing iron content.

Purpose of the Study:

• To evaluate the impact of MRI resolution on QSM-derived iron content measurements.
• To ensure QSM consistency across different field strengths and manufacturers for DGM iron assessment.
• To establish an age-dependent susceptibility baseline for DGM structures.

Main Methods:

• Collected QSM data from 623 healthy adults (20-90 years) across multiple sites and MRI scanners (1.5T and 3.0T).
• Segmented eight subcortical nuclei and analyzed mean susceptibility, volume, and total iron content.
• Correlated iron metrics with age, examining both global and high-iron regions (RII).
• Utilized a digitized brain model to assess the effect of resolution on QSM.

Main Results:

• Slice thickness had minimal impact on QSM in larger DGM structures but reduced susceptibility in smaller ones.
• Mean susceptibility generally increased with age in most DGM structures, with notable exceptions.
• Total iron content increased with age in most structures, despite decreasing volumes.
• Regional analysis of high-iron areas showed moderate to strong age-related correlations.

Conclusions:

• QSM provides reliable, cross-site, and cross-manufacturer estimates of age-related brain iron changes.
• Established susceptibility baselines can aid in correcting for age effects in neurodegenerative disease studies (e.g., Parkinson's, Alzheimer's).
• High-resolution QSM is essential for accurate iron quantification and age-correction.