CSF contamination contributes to apparent microstructural alterations in mild cognitive impairment

Area of Science:

• Neuroimaging
• Neurology
• Biomedical Engineering

Background:

• Diffusion MRI is crucial for detecting microstructural changes in neurological diseases.
• Ageing and neurodegeneration cause atrophy, leading to cerebrospinal fluid contamination (CSFC) artifacts in diffusion MRI.
• Understanding CSFC's influence is vital for accurate disease assessment.

Purpose of the Study:

• To investigate the impact of CSFC on apparent microstructural changes in mild cognitive impairment (MCI).
• To analyze CSFC effects at multiple spatial scales: individual tracts, white matter skeleton, and histograms.
• To evaluate the efficacy of free-water elimination for correcting CSFC-induced artifacts.

Main Methods:

• Diffusion MRI scans were acquired from 25 individuals with MCI and 20 healthy controls.
• A voxel-by-voxel free-water elimination method was employed for post-acquisition CSFC correction.
• Analysis included tract-level, tract-based spatial statistics (TBSS), and white matter histogram approaches.

Main Results:

• CSFC significantly influenced apparent microstructural differences between MCI patients and controls, affecting up to two-thirds of diffusivity measure differences.
• The apparent spatial pattern of white matter involvement in MCI shifted after CSFC correction.
• TBSS showed robustness across most of the white matter skeleton, with localized CSFC effects; fornix microstructure differences were exaggerated by CSFC.

Conclusions:

• CSFC introduces significant quantitative and spatial artifacts in diffusion MRI studies of MCI.
• Free-water elimination is a valuable method for distinguishing true microstructural alterations from volumetric changes caused by atrophy.
• Accurate interpretation of diffusion MRI in atrophic conditions like MCI requires robust CSFC correction.