To compare iron accumulation in various brain regions using quantitative susceptibility mapping (QSM) in Parkinson’s disease (PD) patients without dementia and cognitively intact elderly (CIE).

Susceptibility-based magnetic resonance imaging methods including QSM have shown that iron content is elevated in specific structures in PD including the substantia nigra, globus pallidus, putamen and caudate nucleus. Iron content has also been shown to increase over time in PD patients. QSM could serve as a non-invasive tool to follow the disease course in PD.

Subjects with PD without dementia and CIE were included from the COMPASS study. Images were acquired using a 3T Siemens scanner for QSM. Regions of interest (ROIs) were drawn manually bilaterally by a blinded researcher using single slices in the caudate nucleus, putamen, globus pallidus, thalamus, red nucleus, substantia nigra, and dentate nucleus with the posterior limb of the internal capsule used as a control. Ten subjects were used for repeat ROI tracing to assess intra-rater reliability via the intra-class correlation coefficient (ICC). PD patients (n=29 [20 males, 9 females], average age 66.8 years) were compared to CIE (n=27 [12 males, 15 females], average age 64.4 years) using t-tests for each ROI. Statistical significance was defined as a p-value < 0.05.

ICCs for ROIs were >0.90 (p≤0.001) except for the right globus pallidus for which the ICC was 0.70 (p=0.041), suggestive of mostly excellent intra-rater reliability. When comparing CIE to PD, the only statistically significant ROI was the pulvinar (p=0.026) with the putamen trending to, but not reaching statistical significance (p=0.092).