Water diffusion compartmentation at high b values in ischemic human brain

Area of Science:

• Neuroimaging
• Biophysics
• Stroke research

Background:

• Brain water exists in distinct compartments with varying diffusion rates.
• Understanding these compartments is crucial for diagnosing and monitoring neurological conditions like stroke.

Purpose of the Study:

• To investigate the dynamic changes in brain water compartments during the early stages of ischemic stroke.
• To characterize the diffusion properties of water in healthy and stroke-affected brain tissue.

Main Methods:

• Utilized diffusion-weighted imaging (DWI) at 1.5 T with a biexponential decay model.
• Analyzed signal intensity decay across multiple b values (0-5000 s/mm²) to quantify water diffusion.
• Selected regions of interest in white matter, striatum (healthy), and ischemic core (stroke patients).

Main Results:

• In healthy subjects, fast diffusing compartments (FDC) constituted 74.3% of brain water.
• In early stroke, FDC significantly decreased to 49.1% (P < 1.05x10⁻⁵).
• Slow diffusing compartments (SDC) showed increased apparent diffusion coefficients (ADC) in stroke (P < 8.07x10⁻³), while ADC of FDC remained unchanged.

Conclusions:

• Restricted diffusion in early ischemic stroke is primarily due to water shifting from FDC to SDC.
• This water redistribution signifies a fundamental change in brain tissue microstructure following ischemia.
• DWI analysis of water compartments offers insights into acute stroke pathophysiology.