Atlas-based relaxometry and subsegment analysis of the substantia nigra pars compacta using quantitative MRI: a healthy volunteer study

Objective: Parkinson's disease is a neurodegenerative disorder caused by neuronal cell loss in the substantia nigra pars compacta (SNpc). We aimed to perform atlas-based relaxometry using an anatomical SNpc atlas and obtain baseline values of SNpc regions in healthy volunteers. Methods: Neuromelanin (NM)-sensitive imaging of the midbrain and whole--brain 3D T-1 weighted images of 27 healthy volunteers (20 males; aged 36.3 +/- 11.5 years) were obtained. An anatomical SNpc atlas was created using NM-sensitive images in standard space, and divided into medial (MG), dorsal (DG), and ventrolateral (VG) groups. Proton density (PD), T-1, and T-2 values in these regions were obtained using quantitative MRI. The relationships between PD, T-1, and T-2 values in each SNpc region and age were evaluated. Results: The VG PD value was significantly higher than the MG and DG values. MG, DG, and VG T1 values were significantly different, whereas the T-2 value of the MG was significantly lower than the DG and VG values. Moreover, a significant negative correlation between PD and T-1 values of the MG and age was observed. Conclusion: The PD, T-1, and T-2 values of the SNpc regions measured in standard space using an anatomical atlas can be used as baseline values. PD and T-1 values of the SNpc regions may be associated with NM concentrations. Advances in knowledge: An anatomical SNpc atlas was created using NM-sensitive MRI and can be used for the quantitative evaluation of subsegments of the SNpc in standard space.