Practical obstacles and their mitigation strategies in compressional optical coherence elastography of biological tissues

Abstract

In this paper, we point out some practical obstacles arising in realization of compressional optical coherence elastography (OCE) that have not attracted su±cient attention previously. Speci¯-cally, we discuss (i) complications in quanti¯cation of the Young modulus of tissues related to partial adhesion between the OCE probe and soft intervening reference layer sensor, (ii) distorting in°uence of tissue surface curvature/corrugation on the subsurface strain distribution mapping, (iii) ways of signal-to-noise ratio (SNR) enhancement in OCE strain mapping when periodic averaging is not realized, and (iv) potentially signi¯cant in°uence of tissue elastic nonlinearity on quanti¯cation of its sti®ness. Potential practical approaches to mitigate the e®ects of these complications are also described.

Interplay of temperature, thermal‐stresses and strains in laser‐assisted modification of collagenous tissues: Speckle‐contrast and OCT‐based studies

“…En face speckle processing readily makes it possible to characterize IR‐irradiation‐induced tissue modification over fairly large regions (well matching requirements of implant preparation), albeit without depth resolution and direct strain visualization. Scanning OCT‐based elastography operating with sequences of B‐scans at the same position (for setups and processing methods described in References ) is able to visualize interframe and cumulative strains in real time, providing detailed information on depth dependence and time evolution of strains over B‐scans.…”

“…The experimental procedures were similar to those described in our previous works with the experimental configuration shown in Figure B. The irradiation regime was close to type (a) described in Section 2.1 with characteristic exposure times 4 to 10 seconds and interpulse pauses ~ 2 seconds.…”

“…Such heating‐induced structural rearrangements in avascular collagenous tissue can be conveniently observed, for example, using recently developed methods of OCT‐based imaging of displacements, strains and stiffness distribution in the tissue bulk with fairly high time‐resolution ~10 milliseconds. Scanning OCT‐based imaging also ensures depth‐resolved mapping of the Young modulus distribution (obtaining elastographic B‐scans) .…”

“…The OCT‐based results reported here have the following distinctive features: (a) we are focused on visualization of real‐time spatiotemporal evolution of transient heating‐induced changes in the irradiated samples and (b) we quantitatively visualize earlier inaccessible local thermally induced strains in the tissue bulk using recently developed elastographic OCT‐based technique . Such visualization in the form of elastographic B‐scans can readily be made by analyzing in‐depth structural OCT B‐scans sequentially acquired at the same location.…”

Laser-induced elastic wave classification: thermoelastic versus ablative regimes for all-optical elastography applications

“…10,11 Static approaches are capable of mapping the local two-dimensional and three-dimensional strain distribution with high spatial resolution, including estimation of the nonlinear elastic properties. [10][11][12][13][14][15][16][17][18] In dynamic elastography, the tissue is perturbed by impulsive loading or harmonic vibrations, and the elasticity estimation is based on tissue motion as a function of time, i.e., velocity of the elastic wave or displacement dynamics. [2][3][4] Dynamic approaches permit direct quantification of the absolute values of the elastic constants using appropriate models.…”