Relationship Between Fractional Anisotropy and Negative Susceptibility from Single-orientation Magnetic Susceptibility Separation

The magnetic source separation method can estimate contributions of diamagnetic myelin and paramagnetic iron in the white matter using solely gradient-echo data in white matter. This study determined the relationship between negative susceptibility (χ-) and fractional anisotropy as a myelin-sensitive biomarker and compared with the conventional susceptibility (χ) in young healthy volunteers. There was a significant negative correlation between the χ- and FA. In contrast, the conventional χ has a weaker correlation to the FA than the χ- result. However, the χ- in white matter represented the non-monotonic fiber orientation dependence on the B0 field.