A Rapid Stokes Imaging Method for Characterizing the Optical Properties of Tissue During Immersion Optical Clearing

The diffusion of drugs or agents in biological tissues is vital in biomedicine. Here we propose a non-invasive polarization optical method to evaluate the microstructural changes in tissues during agent diffusion. Skeletal muscle samples immersed in an aqueous solution of glycerol of various concentrations are taken to confirm the performance of the method. Temporal polarized images are captured by a rapid Stokes imaging system, then Stokes parameters s(1), s(2), s(3) are calculated and polarization parameters such as depolarization Delta(c) and linear retardance delta are derived for quantifying tissue changes. By observing polarization parameters in experiments using different concentrations of agents, staged characteristics during tissue optical clearing are extracted. Comparing diffusion properties at different concentrations, we find that the variation of polarization parameters becomes more significant with the increasing concentration. Combined with Monte Carlo simulations, the dominant mechanism in different optical clearing stages in tissues can be explained. Specifically, dehydration dominates in the first stage, and refractive index matching gradually dominates after a transitional stage. The experiments and simulations confirm the potential of rapid Stokes imaging to explore the diffusion properties in biological tissues and give a detailed optical characterization and explanation.