Refractive-index matching enhanced polarization sensitive optical coherence tomography quantification in human brain...

Area of Science:

• Neuroimaging
• Biomedical Optics
• Materials Science

Background:

• Polarization-sensitive optical coherence tomography (PS-OCT) is crucial for human brain imaging, particularly for visualizing white matter architecture.
• Quantifying fine-scale fiber tracts in the human brain cortex (gray matter) remains challenging due to low birefringence.

Purpose of the Study:

• To investigate the impact of refractive index matching using 2,2'-thiodiethanol (TDE) immersion on PS-OCT measurements in ex vivo human brain tissue.
• To assess the improvement in fiber tract visualization and birefringence quantification in both gray and white matter.

Main Methods:

• Applied refractive index matching with TDE immersion to ex vivo human brain tissue samples.
• Utilized PS-OCT to acquire high-resolution images and measure fiber orientation and birefringence.
• Performed mathematical simulations to understand the underlying mechanisms of improvement.

Main Results:

• Successfully mapped fiber orientations of U-fibers, cortical fibers, radial fibers, and laminar structures in gray matter.
• Reduced noise in axis orientation measurements by 56% (white matter) and 39% (gray matter) with index matching.
• Enabled precise birefringence measurements, correcting underestimation (82% in white matter) and overestimation (16% in gray matter).

Conclusions:

• Refractive index matching with TDE significantly enhances PS-OCT capabilities for detailed human brain cortex and white matter imaging.
• The improvements are attributed to reduced tissue scattering and enhanced signal-to-noise ratio, surpassing conventional noise reduction techniques.
• This method offers a pathway for more accurate and detailed analysis of neural pathways and structures.