Backscattering Mueller matrix polarimetry estimates microscale anisotropy and orientation in complex brain tissue...

Area of Science:

• Neuroimaging
• Optical Physics
• Biophysics

Background:

• Diffusion magnetic resonance imaging (dMRI) is crucial for quantifying brain microstructure.
• Diffusion tractography is a key clinical application of dMRI.
• Advanced imaging techniques are needed to validate dMRI findings at a microstructural level.

Purpose of the Study:

• To compare complete backscattering Mueller matrix polarized light imaging (PLI) with dMRI in ferret optic chiasm (OC) tissue.
• To investigate PLI as a dMRI validation tool.
• To understand the microstructural and orientational sensitivity of PLI in varying tissue thicknesses.

Main Methods:

• Post-mortem ferret brain tissue (whole brain and OC) was imaged using dMRI and complete backscattering Mueller matrix PLI.
• Specimens were sectioned and re-imaged with PLI.
• Correlation analyses were performed on scalar metrics and orientation vectors from both imaging modalities.

Main Results:

• Optical retardance and dMRI fractional anisotropy demonstrated correlated trends, suggesting a macroscale architectural bias in retardance.
• Thick tissue analysis revealed comparable orientation between the diattenuation angle (PLI) and dMRI fiber orientation distribution glyphs.
• Orientation information from the retardance angle was less consistent.

Conclusions:

• Backscattering Mueller matrix PLI is a potential tool for validating dMRI microstructural data in thick tissue specimens.
• Complete polarimetry provides directional characterization and microscale anisotropy information beyond conventional PLI.
• This study advances the validation of neuroimaging techniques through multimodal comparison.