Optical coherence elastography for visualization of spatio-temporal strain dynamics in thermo-mechanical modification of corneal and cartilaginous tissues

摘要

In recent years, an emerging group of therapeutic methods, which can be considered as intermediate between photobiomodulationand coagulative methods, is non-surgical thermo-mechanical reshaping of avascular collagenousbiological tissues. It is based on moderate laser-produced heating (below 50-700C) combined with auxiliary mechanicalaction on the tissue. For duly chosen parameters, such moderate heating can be biologically non-destructive, so that thistechnique of laser-assisted modification of collagenous tissues is emerging in clinic for various applications. Forexample, using such an approach, planar cartilaginous plates can be transformed into annulus-shape implants forotolaryngological operations. Similar microsructural changes occurring in moderately heated cornea open the possibilityto modify eye-cornea shape and, consequently, eye refraction, which can be used for non-surgical correction of visionproblems. Such applications obviously require detailed understanding of the background thermo-mechanical propertiesand possibility to precisely control the laser-produced heating and the resultant deformations of the tissue. Recently,progress in the development of optical coherence elastography (OCE), in particular the possibility to obtain highresolutionmaps of "instantaneous" and cumulative strains suggests that OCE can be successfully used as a control meanin the novel applications of laser-assisted tissue reshaping. This study reports results on application of phase-sensitiveoptical coherence elastography for mapping transient thermomechanically-produced strain fields in such biologicaltissues, as cartilages and cornea subjected to pulse-periodic irradiation with infrared Gaussian laser beam. The developedOCE technique made it possible to demonstrate complex character of the thermo-mechanically produced strains, whichis attributed to non-trivial interplay between the spatially non-coinciding temperature increase and thermal stresses.