Abnormal accumulation of Lewy-related pathology in the nervous system has been reported as a key part of the pathological changes in Parkinson’s disease (PD) [1]. The earliest degenerative changes, called Lewy neurites, aggregate at the neurites and are related to neurite loss or structural change [2]. In recent years, multishell diffusion-weighted MRI (dMRI) and neurite-orientation dispersion and density imaging (NODDI) models have allowed researchers to estimate neurite structure and density in the gray matter [3, 4]. The purpose of this study is to use NODDI to quantitatively evaluate neurite degeneration in the gray matter in PD.Multishell dMRI was performed using 3T MRI (Achieva, Philips) on 11 patients with PD and 13 healthy controls matched for age and sex. Multishell dMRI data were acquired with a spin-echo EPI sequence along 32 isotropic diffusion gradient directions. For each direction, Multishell dMRI were acquired with three values of b (0, 1,000, and 2,000 s/mm2). The sequence parameterswere as follows: image orientation, axial; repetition time (TR), 7,041 ms; echo time (TE), 70 ms; diffusion gradient pulse duration (δ), 13.3 ms; diffusion gradient separation (Δ), 45.3 ms; number of excitations (NEX), 1; field of view, 240 mm; matrix, 80×80; slice thickness, 3 mm; number of slices, 50; and imaging time, 6 min 26 s. The intracellular volume fraction (Vic) and orientation dispersion index (OD) were calculated using the NODDI toolbox and the gray matter on the Vic, OD, FA, and MD maps was analyzed by using gray matter-based spatial statistics (GBSS). Region-of-interest (ROI) analysis was added using an ROI template taken from the Harvard-Oxford subcortical and cortical structural atlas.The GBSS results showed a significant decrease in Vic in the right amygdala and right posterior putamen, right hippocampus, right parahippocampal gyrus, right frontal orbital cortex, right temporal pole in the PD group compared with the healthy controls (uncorrected p < 0.0005). No significant change was observed in OD, FA, or MD. ROI analysis also showed a significant decrease in Vic in the right amygdala (p = 0.0017), in the right parahippocampal gyrus (p = 0.0034), but no significant change was observed in the any other area.The amygdala, parahippocampal gyrus is a region where Lewy pathology occurs at the early stages of PD, with Lewy neurite aggregation at the neurites and Lewy body deposits in the cell bodies, accompanied by neuronal loss and degeneration of neurite structures [3]. Because Vic reflects neurite density, the decrease in Vic in the amygdala may indicate a decrease in neurite density in the amygdala of PD patients.The amygdala, parahippocampal gyrus is a region where Lewy pathology occurs at the early stages of PD, with Lewy neurite aggregation at the neurites and Lewy body deposits in the cell bodies, accompanied by neuronal loss and degeneration of neurite structures [3]. Because Vic reflects neurite density, the decrease in Vic in the amygdala may indicate a decrease in neurite density in the amygdala of PD patients.