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Investigation of Apparent Diffusion Coefficient from Ultra-high b-Values in Parkinson's Disease
Ling Xueying1, Zhang Zhongping, Zhao Zhoushe
1Department of Medical Imaging Center, the First Affiliated Hospital, Jinan University, Huangpu West Road, Guangzhou, China.
Objectives:
To assess brain damage in Parkinson's disease (PD) based on apparent diffusion coefficient (ADC) data obtained from ultra-high b-values.
Methods:
Eighteen PD patients and 18 controls received diffusion-weighted imaging (DWI) with standard b-values (0, 1,000 s/mm(2)) and 15 b-values (0-5,000 s/mm(2)). Standard ADC (ADCst) maps were calculated from standard b-values, while maps of pure diffusion coefficients (D), pseudo-diffusion coefficients (D(*)), and ultra-high ADCs (ADCuh) were calculated from the 15 b-values using a tri-component model. In this model, D and D(*) values were quantified with a bi-exponential equation using b-values less than 2,000 s/mm(2), while ADCuh was quantified by fitting the signals at ultra-high b-values (2,000-5,000 s/mm(2)) to the mono-exponential equation. ADCst, ADCuh, D, and D(*) of the globus pallidus (GP), putamen (P), and substantia nigra (SN) were compared between PD patients and normal control subjects.
Results:
ADCuh of the GP, P, and SN was significantly lower in PD patients than those in control subjects (P < 0.001), while ADCst, D, and D(*) of the GP, P and SN were not different between the two groups (P > 0.05).
Conclusions:
ADCuh may be a useful measurement for evaluating brain damage in PD patients.
Key Points:
• DWI with ultra-high b-values may provide new insight into Parkinson's disease pathology • ADC calculated using ultra-high b-values is different between PD and controls • ADC uh may be associated with water transportation by aquaporins.

