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Visualization and Quantification of the Striato-pallidonigral Fibers in Parkinson's Disease Using Diffusion Tensor Imaging

Yu Zhang, Katherine Wu, Shannon Buckley, Norbert Schuff
AD/PD: Florence, Italy
Download Presentation: ADPD2013 yu-zhang f 874e3f20.pdf
Objectives: Striato-pallidonigral fibers play an important role in Parkinson's Disease (PD), but their visualization with tractography based on diffusion tensor imaging (DTI) is difficult and measuring alterations of fiber integrity remains a challenge. This study aimed to reliably identify striato-pallidonigral fibers in DTI data from the Parkinson's Progression Marker Initiative (PPMI), which is a multicenter study that funded by the Michael J. Fox Foundation for Parkinson's Research.
Methods: DTI scans of 16 controls and 18 PD patients were randomly selected from the PPMI data source. Raw DTI images of original 2 mm3 resolution were trilinearly interpolated to 1mm3. Tractography was performed using TrackVis. A 'target' ROI was placed at the putamen/ globus pallidus (Put/GP) and a 'seed' ROI disk, one voxel in size, was placed in the substantia nigra (SN), searching for the best location until the output fibers reach the 'target' at Put/GP.
Results: Tractography consistently showed in all subjects a fiber tract connecting the medial-posterior part of SN and the GP, via the anterior subthalamic nucleus (STN) (Figure). Furthermore, the profiles of DTI indices along the fiber tracts, which we quantified using local linear embedding, an unsupervised statistical learning algorithm, showed systematic differences between patients and controls.
Conclusions: Tracking the striato-pallidonigral fibers in multicenter DTI scans is feasible, facilitating assessments of fiber integrity in PD.