Computational NeuroscienceThe feasibility of quantitative MRI of perivascular spaces at 7Â T

- Perivascular space dilation is associated with many conditions, including aging, dementia, and Alzheimer's disease (AD).
- We performed MRI of whole brain PVS at 7 T. We also developed a computational method to quantify white matter PVS density.
- Our preliminary study confirmed that PVS density is higher in AD patients than healthy subjects.
- Quantitative PVS MRI at 7 T may serve as an imaging biomarker for the Aβ clearance through PVS drainage system.

BackgroundDilated 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 (≤3 T). This study tests the feasibility of imaging and quantifying brain PVS with an ultra-high 7 T whole-body MRI scanner.New method3D high resolution T2-weighted brain images from healthy subjects (n = 3) and AD patients (n = 5) were acquired on a 7 T 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.ResultsThe 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 methodWe demonstrated that 7 T provides sufficient SNR and resolution for quantitatively measuring PVSs in deep white matter that is challenging with clinical MRI systems (≤3 T). Compared to the conventional visual counting and rating for the PVS assessment, the quantitation method we developed is automatic and objective.ConclusionsQuantitative PVS MRI at 7 T may serve as a non-invasive and endogenous imaging biomarker for diseases with PVS dilation.

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