Imaging cell size and permeability in biological tissue using the diffusion-time dependence of the apparent diffusion...

Area of Science:

• Biophysics
• Biomolecular Engineering
• Medical Imaging

Background:

• Understanding water diffusion in biological tissues is crucial for characterizing cellular structures.
• Previous models often require complex parameterization, limiting their application.

Purpose of the Study:

• To develop and validate a simplified, dimensionless model for restricted water diffusion.
• To enable accurate cell-size and membrane permeability measurements using diffusion MRI.

Main Methods:

• A dimensionless model was derived based on diffusion distances in a system of permeable membranes.
• Diffusion coefficients were measured in carrot tissue using diffusion-weighted MRI across multiple diffusion times.
• The model was evaluated by numerically calculating dimensionless diffusion coefficients and fitting experimental data.

Main Results:

• The derived dimensionless model accurately predicts water diffusion behavior.
• Key tissue parameters, including cell size (21-76 μm), permeability (0.007-0.039 μm⁻¹), and free diffusivity (1354-1713 μm²/s), were determined.
• Cell size measurements from dMRI showed good agreement with light microscopy.

Conclusions:

• The proposed dimensionless model offers a robust method for determining tissue parameters (D0, L, P) using multi-time diffusion MRI.
• This approach provides a valuable tool for non-invasive assessment of biological tissue characteristics.