Numerous attempts have been made to visualize substructure morphology of the SN and to assess the neurodegenerative changes using various magnetic resonance imaging (MRI) signal contrasts23. For example, iron-sensitive MR sequences have great potential to define the boundaries and shape of the SN234 as the local deposition of iron alters magnetic field inhomogeneities and appears hypointense in T2 or T2*-weighted images (T2*WI) due to the shortening of transverse relaxation times25. By taking advantage of region-specific iron content within the SN, the area of lower T2*-weighted signal intensity is assigned to the SNr based on the histological observation of elevated iron concentration in that region356. NM-sensitive T1-weighted fast spin echo technique in in vivo 3T MRI studies allows the visualization of the SNc via hyperintense areas23789. NM within the dopaminergic neurons is speculated to generate paramagnetic T1-shortening effects on combining with metals, such as iron and copper23710. While NM-containing dopaminergic neurons are densely distributed in the SNc, they form clusters of cells that penetrate deep into the caudal part of the SNr. Thus, it may not be easy to delineate the boundaries between the SNc and the SNr with the use of NM-sensitive T1-weighted MRI alone3.