Visualizing kinetics of diffusional penetration in tissues using OCT-based strain imaging

We report a new application of the recently developed technique, Optical Coherence Elastography (OCE) to quantitatively visualize kinetics of osmotic strains due to diffusive penetration of various osmotically active solutions into biological tissues. The magnitude of osmotic strains may range from fractions of one per cent to tens per cent. The visualized spatio-tempotal dynamics of the strains reflect the rates of osmotic dehydration and diffusional penetration of the active solute, which can be controlled by concentration of the solution components. Main features of the OCE-visualized diffusion-front dynamics well agree with Fick's theory yielding diffusivity coefficients consistent with the literature data. The OCE technique may be used to study diffusion of a broad variety of osmotically-active substances - drugs, cosmetic agents, preservative solutions, so-called optical clearing agents enhancing the depth of optical visualization, etc. The corresponding experimental examples, some results of theoretical interpretations and numerical simulations are given.