Using Multimodal Imaging to Investigate the Relationship Between Iron, Myelin, and MRI Relaxation

Motivation: MRI relaxation mapping can spatially quantify iron content in patients with neurodegenerative disease, but is confounded by variability in other tissue components, most notably myelin. Goal(s): To estimate the relative contributions of iron and myelin to MRI relaxation, by performing a pixel-wise, multi-modality correlation of iron and myelin with MRI. Approach: Human Alzheimer's disease brain sections underwent 50um2 resolution MRI, quantification of myelin using Raman Imaging, and iron using SRXRF. Spatial relationships were investigated by multiple linear regression. Results: Iron, and myelin coefficients were consistent between groups, but more variable in Alzheimer's disease. Raman imaging was demonstrated as a quantitative myelin mapping method. Impact: This work applies SRXRF and Raman imaging to estimate the contributions of iron and myelin to MRI relaxation. The results can be utilised to increase the specificity of MRI relaxation mapping measurements to iron.