Inferring microstructural features and the physiological state of tissues from diffusion-weighted images

Area of Science:

• Medical Imaging
• Biophysics
• Neuroimaging

Background:

• Diffusion weighted images (DWIs) are crucial for non-invasively probing tissue microstructure.
• Understanding water diffusion in biological tissues requires advanced imaging techniques.
• Isotropic and anisotropic tissue properties necessitate distinct analytical approaches.

Purpose of the Study:

• To review methods for inferring microstructural and physiological information from DWIs.
• To highlight the capabilities of Diffusion Imaging (DI) and Diffusion Tensor Imaging (DTI).
• To explain the principles behind characterizing water diffusion in various tissue types.

Main Methods:

• Review of Diffusion Imaging (DI) techniques.
• Detailed examination of Diffusion Tensor Imaging (DTI) for anisotropic tissues.
• Discussion of isotropically weighted imaging and q-space imaging.
• Utilizing geometrical constructs like the diffusion ellipsoid.
• Explaining relevant Nuclear Magnetic Resonance (NMR) experiments.

Main Results:

• DI provides one-dimensional diffusion information for isotropic tissues.
• DTI offers three-dimensional diffusion information essential for anisotropic tissues.
• DTI generates scalar parameters (e.g., Trace(D)) acting as quantitative diffusion 'stains'.
• Parameters derived from the diffusion tensor (D) characterize anisotropic diffusion features.

Conclusions:

• DI and DTI are powerful tools for tissue characterization using DWIs.
• DTI significantly enhances the understanding of complex diffusion in anisotropic environments.
• Diffusion ellipsoid models and NMR experiments aid in interpreting diffusion data.