Optimization of phase-resolved optical coherence elastography for highly-sensitive monitoring of slow-rate strains

A realization of real-time optical coherence elastography for mapping small-amplitude, slowly varying strains is discussed. The technique is based on the recently developed 'vector' method for estimating interframe phase-variation gradients by considering complex-valued signals in optical coherence tomography (OCT) as vectors in the complex plane. This method is very tolerant to various measurement noises and allows for mapping both fairly fast and large, as well as rather small and slow-rate strains. Evaluation of strains slowly varying on intervals of ~tens of minutes is important for the emerging techniques of laser-assisted modification of collagenous tissues (e.g. for estimating post-reshaping stability of laser-modeled cartilaginous implants) or for studying slow deformations of osmotic origin in biological tissues. Optimization of the interframe interval for improving signal-to-noise ratio (SNR) in OCE-mapping of slowly-varying strains is discussed and experimentally demonstrated. The ultimate stability of strain estimation with the designed OCT setup is experimentally estimated using stable phantoms. Examples of the spatially resolved maps of slowly-varying strains are presented.