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The feasibility of quantitative MRI of perivascular spaces at 7T
Kejia Cai1, Rongwen Tain1, Sandhitsu Das2
1Department of Radiology, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA; Center for MR Research, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
Background:
Dilated brain perivascular spaces (PVSs) are found to be associated with many conditions, including aging, dementia, and Alzheimer's disease (AD). Conventionally, PVS assessment is mainly based on subjective observations of the number, size and shape of PVSs in MR images collected at clinical field strengths (≤3T). This study tests the feasibility of imaging and quantifying brain PVS with an ultra-high 7T whole-body MRI scanner.
New Method:
3D high resolution T2-weighted brain images from healthy subjects (n=3) and AD patients (n=5) were acquired on a 7T whole-body MRI scanner. To automatically segment the small hyperintensive fluid-filling PVS structures, we also developed a quantitative program based on algorithms for spatial gradient, component connectivity, edge-detection, k-means clustering, etc., producing quantitative results of white matter PVS volume densities.
Results:
The 3D maps of automatically segmented PVS show an apparent increase in PVS density in AD patients compared to age-matched healthy controls due to the PVS dilation (8.0±2.1 v/v% in AD vs. 4.9±1.3 v/v% in controls, p<0.05).
Comparison With Existing Method:
We demonstrated that 7T provides sufficient SNR and resolution for quantitatively measuring PVSs in deep white matter that is challenging with clinical MRI systems (≤3T). Compared to the conventional visual counting and rating for the PVS assessment, the quantitation method we developed is automatic and objective.
Conclusions:
Quantitative PVS MRI at 7T may serve as a non-invasive and endogenous imaging biomarker for diseases with PVS dilation.
Insights
Ultra-high 7T MRI enables quantitative measurement of dilated brain perivascular spaces (PVSs). This advanced imaging technique offers an objective, automated method for assessing PVSs, potentially serving as a biomarker for diseases like Alzheimer's.
Area of Science:
- Neuroimaging
- Radiology
- Biomarkers
Background:
- Dilated brain perivascular spaces (PVSs) are linked to aging, dementia, and Alzheimer's disease (AD).
- Current PVS assessment relies on subjective analysis of MR images at clinical field strengths (≤3T).
Purpose of the Study:
- To test the feasibility of imaging and quantifying brain PVSs using an ultra-high 7T MRI scanner.
- To develop an automated method for PVS quantification.
Main Methods:
- Acquired 3D high-resolution T2-weighted brain images from healthy subjects (n=3) and AD patients (n=5) on a 7T MRI scanner.
- Developed a quantitative program using spatial gradient, component connectivity, and edge-detection algorithms for automatic PVS segmentation.
- Calculated white matter PVS volume densities.
Main Results:
- Automatically segmented PVS maps revealed significantly higher PVS density in AD patients (8.0±2.1 v/v%) compared to healthy controls (4.9±1.3 v/v%).
- Observed PVS dilation in AD patients, correlating with increased PVS density.
Conclusions:
- 7T MRI provides sufficient signal-to-noise ratio and resolution for quantitative PVS measurement in deep white matter, surpassing clinical MRI systems (≤3T).
- The developed quantitative method is automatic and objective, offering an improvement over conventional visual PVS assessment.
- Quantitative PVS MRI at 7T shows promise as a non-invasive imaging biomarker for diseases characterized by PVS dilation.
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