Atlas-Guided Tractography for Segmentation of Striatal Subregions in Early Parkinson’s Disease

Parkinson’s disease (PD) and isolated REM sleep behaviour disorder (iRBD) are neurodegenerative conditions associated with alterations in the striatum, a subcortical structure essential for motor and cognitive functions. In this study, we apply diffusion tensor imaging (DTI) and probabilistic tractography to segment the striatum into two functionally distinct compartments: striosomes and matrix. A total of 152 subjects were included: 64 PD patients, 47 iRBD patients, and 41 healthy controls. Preprocessing, tractography, and segmentation were performed using the FSL toolbox; voxel-based morphometry (VBM) was used for group comparisons. Probabilistic group atlases were constructed in MNI space and compared with each other and with the standard MNI_152 atlas using RMSE and statistical testing. Results show significant differences in the matrix region, particularly in the right striatum of iRBD subjects compared to both PD and control groups. Our findings suggest that connectivity-based striatal segmentation may reflect early structural changes in neurodegeneration and could support future biomarker development for PD and related disorders. This tractography-based approach offers a promising tool for the personalized analysis of subcortical brain structures in clinical neuroimaging.