Probing bio-tissue films by optical internal reflectivity: modeling and measurements

Area of Science:

• Biophysics
• Optical Physics
• Materials Science

Background:

• Optical properties of biological tissues are crucial for understanding their structure and function.
• Existing effective medium theories offer a basic understanding but lack precision for complex bio-tissue films.
• Confined bio-tissue films, like whole blood, present unique optical challenges due to their layered cellular structure.

Purpose of the Study:

• To develop a theoretical model for optical reflectivity of bio-tissue films.
• To validate the model against experimental data of confined whole-blood films.
• To assess the model's capability in determining microstructural parameters with high precision.

Main Methods:

• Development of a theoretical model based on the anomalous-diffraction approximation.
• Numerical exploration of model predictions and comparison with effective medium theories.
• Experimental measurement of reflectivity-versus-angle-of-incidence for confined whole-blood films using internal reflection.
• Fitting the theoretical model to experimental data.

Main Results:

• The developed model accurately predicts optical reflectivity of bio-tissue films.
• Experimental results confirm the model's validity, showing precise determination of microstructural parameters.
• Refractive indices of cells and surrounding medium can be determined with better than 1% precision.
• Coherent reflectance measurements with reflectivity around 0.3 exhibit errors below 2%.

Conclusions:

• The theoretical model provides a robust framework for analyzing optical reflectivity of bio-tissue films.
• The model enables precise inference of microstructural parameters from experimental reflectivity data.
• This approach is valuable for monitoring physical changes in bio-tissue films during physicochemical processes.