Magnetic susceptibility source separation for myelin imaging

Imaging myelin has been a long-standing objective of MRI. A recent advancement in quantitative susceptibility mapping (QSM), susceptibility source separation, enables the differentiation of para- and diamagnetic susceptibility sources that co-exist in a voxel, providing information regarding the underlying microstructure. In particular, the method has the potential to reveal the two primary sources of magnetic susceptibility in the brain—iron and myelin—which are known to be related to the pathogenesis of multiple neurodegenerative disorders, such as multiple sclerosis (MS). In this presentation, I will review the method of magnetic susceptibility source separation that has been applied to MS, with a focus on chi-separation. I will then highlight studies that have demonstrated the relationship between diamagnetic susceptibility and myelin content in the brain. Finally, I will conclude by discussing potential artifacts that may obscure the interpretation of diamagnetic susceptibility as it relates to myelin.