  In MRI, researchers have long endeavored to effectively visualize myelin
distribution in the brain, a pursuit with significant implications for both
scientific research and clinical applications. Over time, various methods such
as myelin water imaging, magnetization transfer imaging, and relaxometric
imaging have been developed, each carrying distinct advantages and limitations.
Recently, an innovative technique named as magnetic susceptibility source
separation has emerged, introducing a novel surrogate biomarker for myelin in
the form of a diamagnetic susceptibility map. This paper comprehensively
reviews this cutting-edge method, providing the fundamental concepts of
magnetic susceptibility, susceptibility imaging, and the validation of the
diamagnetic susceptibility map as a myelin biomarker that indirectly measure
myelin content. Additionally, the paper explores essential aspects of data
acquisition and processing, offering practical insights for readers. A
comparison with established myelin imaging methods is also presented, and both
current and prospective clinical and scientific applications are discussed to
provide a holistic understanding of the technique. This work aims to serve as a
foundational resource for newcomers entering this dynamic and rapidly expanding
field.
