Microstructural gradients of magnetic susceptibility in the substantia nigra in Parkinson’s disease using QSM and spatial gradients analysis

Motivation: Aberrant iron accumulation in the substantia nigra (SN) is implicated in Parkinson's disease (PD), but previous studies failed to map the spatial changes (gradients) of magnetic susceptibility in the SN for PD patients. Goal(s): This study aimed to quantify magnetic susceptibility gradients in the SN in PD using quantitative susceptibility mapping (QSM) and spatial gradients analysis. Approach: The approach involved calculating QSM maps, QSM source separation via the APART-QSM, and microstructural gradient analysis of the SN along three axes. Results: Spatially-dependent patterns of magnetic susceptibility in the SN were observed, with abnormal gradients mostly from diamagnetic susceptibility sources of PD patients. Impact: The application of QSM source separation and spatial gradients analysis provides a novel insight for the spatially varying magnetic susceptibility in the SN of PD patients in vivo, which is conducive for understanding the function of the SN in PD.