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Re-examining age-related differences in white matter microstructure with free-water corrected diffusion tensor
Jordan A Chad1, Ofer Pasternak2, David H Salat3
1Rotman Research Institute, Baycrest Health Sciences, Toronto, Ontario, Canada; Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.
Neurobiology of Aging
|August 27, 2018
Summary
Free water in brain white matter (WM) may skew aging studies. Eliminating this free water compartment reveals less pronounced WM microstructural changes and better age correlation with free water fraction.
Area of Science:
- Neuroimaging
- Neuroscience
- Biomedical Engineering
Background:
- Diffusion tensor imaging (DTI) is widely used to study white matter (WM) microstructural changes in aging.
- Aging-related shrinkage of WM fibers increases interstitial spaces, potentially biasing DTI metrics with free water molecules.
- Current DTI analyses may overestimate age-related WM alterations due to extracellular free water.
Purpose of the Study:
- To investigate the impact of extracellular free water on DTI metrics of brain aging.
- To re-evaluate age-related WM microstructural changes after accounting for the free water compartment.
- To determine if free water fraction correlates better with age than conventional DTI parameters.
Main Methods:
- Utilized a cohort of 212 participants for DTI analysis.
- Implemented a method to eliminate the free water compartment from DTI data.
- Compared DTI parameters before and after free water elimination.
- Correlated DTI metrics and free water fraction with participant age.
Main Results:
- WM microstructural changes in aging appear less pronounced after eliminating the free water compartment.
- Post-elimination DTI parameters align with histological findings of myelin degradation and debris accumulation.
- The fraction of free water demonstrated a stronger association with age compared to conventional DTI parameters.
Conclusions:
- Accounting for free water in DTI analyses provides a more accurate assessment of age-related WM changes.
- Free water elimination refines the understanding of brain aging processes.
- Future DTI studies on brain aging can benefit from incorporating free water analysis for novel insights.
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