Measuring iron in the brain using quantitative susceptibility mapping and X-ray fluorescence imaging

Area of Science:

• Neuroimaging
• Neurochemistry
• Medical Physics

Background:

• Iron accumulation in the brain is linked to neurodegenerative diseases.
• Quantitative susceptibility mapping (QSM) is a magnetic resonance imaging (MRI) technique used to estimate iron concentration.
• Validating QSM against established iron quantification methods is crucial for its clinical application.

Purpose of the Study:

• To correlate magnetic susceptibility measurements from QSM with direct iron content measurements.
• To establish the reliability of QSM for quantifying brain iron in vivo and post mortem.
• To assess the potential clinical utility of QSM for diagnosing iron-related neurological conditions.

Main Methods:

• Magnetic susceptibility was measured using QSM derived from MRI data.
• Total iron content was quantified using X-ray fluorescence (XRF) imaging and inductively coupled plasma mass spectrometry (ICPMS).
• The relationship between magnetic susceptibility and iron concentration was statistically analyzed.

Main Results:

• A strong correlation was observed between QSM-derived magnetic susceptibility and iron content measured by XRF and ICPMS.
• The estimated relationship between susceptibility and ferritin iron was 1.10±0.08 ppb susceptibility per microg iron/g wet tissue.
• This relationship is consistent with previous findings in both fixed and unfixed human brain tissue.

Conclusions:

• Magnetic susceptibility measured by QSM provides a direct, reliable, and quantitative assessment of brain iron content.
• QSM is a promising non-invasive imaging biomarker for iron quantification in neurological disorders.
• QSM can be clinically implemented, especially in brain regions with significant iron deposition.