Target audience: Researchers and clinicians interested in Parkinson Disease and brain tissue microstructure. Purpose The T2* map in Enhanced Gradient Echo T2 Star Weighted Angiography (ESWAN) is a sensitive marker of iron overload in brain, especially gray matter; Diffusion Kurtosis Imaging (DKI) may better reflect microstructure change in gray matter than Diffusion Tensor Imaging (DTI) does 1. It has been shown that PD patients feature iron overload in substantia nigra and red nucleus which are located inside the midbrain, and meanwhile encephalatrophy was observed in three different levels--cortex, basal ganglia and midbrain1. The iron overload in substantia nigra considered as a main cause of apoptosis of dopaminergic neuron pathologically, it impacts the release of dopamine to corpus striatum and head of caudate nucleus which located in the basal ganglia area. To explore the relationship between iron overload and microstructure change in the latter two levels, we compare and correlate the parameters from DKI and ESWAN in extrapyramidal systemic nuclei of PD patients and healthy controls to. Methods This prospective study was approved by the hospital ethics committee. Thirty-five cases of clinically confirmed PD patients were included (18 males and 17 females, mean age 67.00±8.76 years), consent forms were obtained. Twenty-three age and gender matched healthy volunteers were recruited as control group (12 males, 11 females, mean age 66.48±5.2 years). All subjects underwent MRI scans including T1WI，T2WI，T2 FLAIR, DKI (TR/TE 10000/107ms; Section Thickness : 4mm; Intersection Gap : 0mm; FOV 24×24cm2; Matrix Size 128×128) and ESWAN (TR/TE : 53/20ms; Section Thickness : 2mm; Intersection Gap : 0mm; FOV : 24×24cm2; Matrix Size : 512×512) on a 3.0T whole body scanner. Bilateral MK value, Ka value, Kr value, MD value, Da value, Dr value and FA value were manually measured on the head of caudate nucleus, putamen, globus pallidus, red nucleus and substantia nigra. The regions of interests were defined by an experienced radiologist with reference to T1WI. The DKI and SWI parameter values of each nucleus were compared between groups by Independent Samples T-test. The correlation between DKI and SWI parameters of each nucleus in PD group was calculated using Spearman Correlation. Results and Discussion The parameters from ESWAN and DKI of a typical PD patient are shown in Fig.1. The correlation between DKI parameters (Kr, Da, FA) and ESWAN parameters are shown in Fig.2. Compared to the HC group, MK value in substantia nigra of PD patients significantly decreased while markedly increased in globus pallidus; Ka value decreased in red nucleus, substantia nigra; Kr value decreased in puteman and red nucleus while increased in globus pallidus and substantia nigra. MD value significantly increased in putamen, globus pallidus, red nucleus and substantia nigra; Da value increased inglobus pallidus, red nucleus and substantia nigra; Dr value increased in inglobus pallidus and substantia nigra. FA value in PD group significantly decreased in putamen while increased in globus pallidus and red nucleus. The Phase value decreased in substantia nigra, red nucleus, globus pallidus and the head of caudate nuclei while increased in putamen(all P＜0.05). Positive correlation was found between the Phase and Kr value in substantia nigra (r=0.349, P=0.030) and the Phase and Da value in red nucleus (r=0.414, P=0.009); meanwhile, negative correlation was found between the Phase and FA value in left putamen. These suggest that iron overload in gray matters, especially the substantia nigra lead to microstructure change, due to neuron apoptosis and demyelination, and then the microstructure change, may inversely add iron overload. Discussion and conclusion In this study, correlations of ESWAN and DKI derived parameters were observed in substantia nigra, red nucleus and putamen in PD patients. It indicates there is connection between the known iron overload and micro-structure changes. This observation may provide further insight of the pathological progression of Parkinson disease.

Acknowledgements

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References

1. Gorell JMet al.Neurology 1995; [2]. Cho ZHet al. Mov Disord2011.