Microstructure-informed slow diffusion tractography in humans enhances visualisation of fibre pathways

Area of Science:

• Neuroimaging
• Diffusion MRI
• White Matter Tractography

Background:

• Conventional diffusion tensor imaging (DTI) uses low b-values, limiting detailed white matter analysis.
• High b-value diffusion tensor analysis reveals a slow diffusion component potentially representing axonal water fraction.
• Previous methods show higher fractional anisotropy in the slow diffusion component than conventional DTI.

Purpose of the Study:

• To investigate the feasibility and benefits of microstructure-informed whole-brain slow-diffusion fibre tracking (SDIFT) in humans.
• To compare SDIFT with conventional DTI for white matter tract visualization and quantification.

Main Methods:

• Acquisition of in vivo diffusion-weighted images in humans up to 6000s/mm² at 3T.
• Reconstruction of fast and slow diffusion tensors using bi-exponential tensor decomposition.
• Deterministic streamlining using the major eigenvector of the slow diffusion tensor for fibre tract visualization.

Main Results:

• SDIFT demonstrated significantly higher counts of long association fibres.
• SDIFT enabled reconstruction of more short association fibres compared to conventional DTI.
• Enhanced visualization and reliability of fibre pathways, particularly in precortical areas with low anisotropy.

Conclusions:

• Microstructure-informed SDIFT is a valuable complementary method for enhancing white matter tractography.
• SDIFT offers improved visualization and reliability, especially in challenging areas like precortical regions.
• Potential applications include assessing axonal integrity, surgical planning, and evaluating cortical connectivity.