The aim of this study was to perform an accurate quantification/topography of NM in the SNc and LC and iron in the SNc and RN, using an automated brainstem atlas-based segmentation pipeline (3D-ABSP) optimized from previous work15, in order to elucidate the NM and iron content patterns in LRRK2-PD and iPD. The gene discussed is LRRK2; the disease is Parkinson disease.