Diffusion kurtosis imaging detects cortical microstructural alterations in amyloid-positive MCI patients

Area of Science:

• Neuroimaging
• Biomarkers
• Alzheimer's Disease Research

Background:

• Alzheimer's disease (AD) is marked by early amyloid-beta (Aβ) plaques and tau pathology, preceding neurodegeneration and cognitive decline.
• Detecting microstructural brain changes linked to Aβ deposition before atrophy is crucial for early AD diagnosis and intervention.

Purpose of the Study:

• Investigate if diffusion kurtosis imaging (DKI) can detect early microstructural alterations in gray matter (GM) associated with Aβ pathology in individuals with mild cognitive impairment (MCI).

Main Methods:

• Utilized DKI-derived metrics, mean kurtosis (MK) and mean diffusivity (MD), to assess cortical and subcortical microstructure in 67 participants (23 cognitively normal [CN], 44 MCI).
• Quantified Aβ burden using 11C-PiB PET imaging and evaluated cortical atrophy, hippocampal volume, and white matter hyperintensities (WMH).

Main Results:

• Aβ-positive MCI patients showed significantly elevated cortical MK, especially in the left lateral temporal lobe and right precuneus, compared to CN and Aβ-negative MCI groups.
• Cortical MK positively correlated with Aβ burden in parietal and temporal cortices, independent of cortical atrophy.
• Mean diffusivity (MD) had weaker associations with Aβ and was more influenced by age; no significant subcortical MK or MD differences were found.

Conclusions:

• Elevated MK in Aβ-positive MCI patients indicates DKI's ability to detect early microstructural changes related to amyloid pathology before cortical atrophy onset.
• Mean kurtosis (MK) shows potential as a non-invasive biomarker for identifying prodromal AD and monitoring disease progression.