Age- and gender-related changes in the normal human brain using hybrid diffusion imaging (HYDI)

Area of Science:

• Neuroimaging
• Biophysics
• Gerontology

Background:

• Diffusion tensor imaging (DTI) is crucial for studying brain aging and diseases.
• Limited research exists on high b-value diffusion imaging and aging effects.
• Biological water diffusion is biexponential, a factor not well-explored in aging studies.

Purpose of the Study:

• To investigate the impact of normal aging on diffusion imaging measures using higher b values.
• To explore biexponential diffusion characteristics in relation to age.
• To compare the sensitivity of various diffusion measures to aging.

Main Methods:

• Employed hybrid diffusion imaging (HYDI) with five q-space shells (b values 0-9375 s/mm²).
• Analyzed 52 healthy subjects aged 18-72 years.
• Utilized region-of-interest and voxel-based analyses for quantitative diffusion measures, including biexponential parameters and DTI metrics.

Main Results:

• Biexponential diffusion measures (fast diffusion fraction f(1), fast diffusivity D(1), axial diffusivity D(a)) showed higher age sensitivity.
• The biexponential volume fraction f(1) demonstrated the most widespread age dependence in voxel-based analysis.
• Fractional anisotropy (FA) and mean diffusivity (MD) changes were observed in frontal white matter, suggesting age-related decline.

Conclusions:

• High b-value, biexponential diffusion analysis offers greater sensitivity to normal brain aging than conventional DTI.
• The fast diffusion compartment fraction (f(1)) is a promising biomarker for tracking age-related white matter changes.
• Findings highlight the potential of advanced diffusion imaging techniques for understanding brain aging dynamics.