Diffusion MRI in the cortex of the brain: Reducing partial volume effects from CSF and white matter in the mean...

Area of Science:

• Neuroimaging
• Diffusion MRI

Background:

• Mean diffusivity (MD) reflects cortical microstructure but is affected by partial volume effects with cerebrospinal fluid (CSF) and white matter (WM).
• Existing methods for reducing partial volume effects have limitations and can introduce bias.

Purpose of the Study:

• To investigate existing and novel approaches for reducing partial volume effects in cortical MD measurements.
• To develop a more precise method for mapping cortical MD, reducing bias from CSF and WM.

Main Methods:

• Proposed a novel approach using high b-value diffusion MRI with spherical b-tensor encoding and super-resolution reconstruction.
• Investigated the novel approach alongside established methods like inversion recovery and free water elimination.
• Validated the methods using both simulations and in vivo data.

Main Results:

• The novel approach significantly reduced partial volume effects with CSF compared to conventional MRI, decreasing maximum errors in simulations from 0.51 to 0.01 μm²/ms.
• In vivo, the median absolute deviation of cortical MD decreased from 0.17 to 0.06 μm²/ms.
• Established methods introduced bias from CSF, WM, or model assumptions, while the novel method showed superior performance.

Conclusions:

• High b-value diffusion MRI with spherical b-tensor encoding and super-resolution reconstruction enables high-precision mapping of cortical MD.
• This advanced technique effectively reduces the influence of partial volume effects with CSF and WM.
• The findings offer a more accurate way to assess cortical microstructure and potential pathology.