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Published on: June 26, 2013
R2* relaxometry analysis for mapping of white matter alteration in Parkinson's disease with mild cognitive impairment
Hirohito Kan1, Yuto Uchida2, Yoshino Ueki3
1Department of Integrated Health Sciences, Nagoya University Graduate School of Medicine, Japan; Department of Radiology, Nagoya City University, Graduate School of Medical Sciences, Japan.
Background:
R2* relaxometry analysis combined with quantitative susceptibility mapping (QSM), which has high sensitivity to iron deposition, can distinguish microstructural changes of the white matter (WM) and iron deposition, thereby providing a sensitive and biologically specific measure of the WM owing to the changes in myelin and its surrounding environment. This study aimed to explore the microstructural WM alterations associated with cognitive impairment in patients with Parkinson's disease (PD) using R2* relaxometry analysis combined with QSM.
Materials And Methods:
We enrolled 24 patients with PD and mild cognitive impairment (PD-MCI), 22 patients with PD and normal cognition (PD-CN), and 19 age- and sex-matched healthy controls (HC). All participants underwent Montreal Cognitive Assessment (MoCA) and brain magnetic resonance imaging, including structural three-dimensional T1-weighted images and multiple spoiled gradient echo sequence (mGRE). The R2* and susceptibility maps were estimated from the multiple magnitude images of mGRE. The susceptibility maps were used for verifying iron deposition in the WM. The voxel-based R2* of the entire WM and its correlation with cognitive performance were analyzed.
Results:
In the voxel-based group comparisons, the R2* in the PD-MCI group was lower in some WM regions, including the corpus callosum, than R2* in the PD-CN and HC groups. The mean susceptibility values in almost all brain regions were negative and close-to-zero values, indicating no detectable paramagnetic iron deposition in the WM of all subjects. There was a significant positive correlation between R2* and MoCA in some regions of the WM, mainly the corpus callosum and left hemisphere.
Conclusion:
R2* relaxometry analysis for WM microstructural changes provided further biologic insights on demyelination and changes in the surrounding environment, supported by the QSM results demonstrating no iron existence. This analysis highlighted the potential for the early evaluation of cognitive decline in patients with PD.
Insights
White matter changes in Parkinson's disease (PD) are linked to cognitive decline. R2* relaxometry revealed microstructural alterations in white matter, potentially aiding early detection of cognitive impairment in PD patients.
Area of Science:
- Neuroimaging
- Neuroscience
- Biomedical Engineering
Background:
- Parkinson's disease (PD) is associated with white matter (WM) microstructural changes.
- Cognitive impairment is a common non-motor symptom in PD.
- R2* relaxometry and quantitative susceptibility mapping (QSM) offer sensitive measures of WM integrity and iron deposition.
Purpose of the Study:
- To investigate microstructural WM alterations in PD patients with and without cognitive impairment.
- To correlate WM changes with cognitive performance using R2* relaxometry and QSM.
- To assess the potential of these MRI techniques for early detection of cognitive decline in PD.
Main Methods:
- Recruited 24 PD patients with mild cognitive impairment (PD-MCI), 22 PD patients with normal cognition (PD-CN), and 19 healthy controls (HC).
- Utilized brain MRI including T1-weighted and multi-echo gradient echo sequences for R2* and QSM analysis.
- Performed voxel-based analysis of R2* values in WM and correlated findings with Montreal Cognitive Assessment (MoCA) scores.
Main Results:
- PD-MCI patients showed lower R2* values in specific WM regions, such as the corpus callosum, compared to PD-CN and HC groups.
- Quantitative susceptibility mapping (QSM) indicated no significant iron deposition in the WM across all participants.
- A positive correlation was observed between R2* values and MoCA scores in WM regions, notably the corpus callosum and left hemisphere.
Conclusions:
- R2* relaxometry effectively detects WM microstructural changes, indicative of demyelination and environmental alterations, in PD patients.
- The absence of iron deposition in WM was confirmed by QSM.
- These findings suggest R2* relaxometry combined with QSM holds promise for the early evaluation of cognitive decline in Parkinson's disease.
