Investigation of Apparent Diffusion Coefficient from Ultra-high b-Values in Parkinson’s Disease

AbstractObjectivesTo assess brain damage in Parkinson’s disease (PD) based on apparent diffusion coefficient (ADC) data obtained from ultra-high b-values.MethodsEighteen PD patients and 18 controls received diffusion-weighted imaging (DWI) with standard b-values (0, 1,000 s/mm2) and 15 b-values (0–5,000 s/mm2). 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/mm2, while ADCuh was quantified by fitting the signals at ultra-high b-values (2,000–5,000 s/mm2) 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.ResultsADCuh 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).ConclusionsADCuh 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 • ADCuhmay be associated with water transportation by aquaporins