Large-field-of-view optical elastography using digital image correlation for biological soft tissue investigation

Abstract

, "Large-field-of-view optical elastography using digital image correlation for biological soft tissue investigation," J. Med. Imag. 4(1), 014505 (2017), doi: 10.1117/1.JMI.4.1.014505. Abstract. In minimally invasive surgery the haptic feedback, which represents an important tool for the localization of abnormalities, is no longer available. Elastography is an imaging technique that results in quantitative elastic parameters. It can hence be used to replace the lost sense of touch, as to enable tissue localization and discrimination. Digital image correlation is the chosen elastographic imaging technique. The implementation discussed here is clinically sound, based on a spectrally engineered illumination source that enables imaging of biological surface markers (blood vessels) with high contrast. Mechanical loading and deformation of the sample is performed using a rolling indenter, which enables the investigation of large organs (size of kidney) with reduced measurement time compared to a scanning approach. Furthermore, the rolling indentation results in strain contrast improvement and an increase in detection accuracy. The successful application of digital image correlation is first demonstrated on a silicone phantom and later on biological samples. Elasticity parameters and their corresponding four-dimensional distribution are generated via solving the inverse problem (only two-dimensional displacement field and strain map experimentally available) using a well-matched hyperelastic finite element model. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Soft tissue elastography via shearing interferometry

“…But because shearing in z-direction is not possible, the gradients ∂u∕∂z, ∂v∕∂z, ∂w∕∂z cannot be determined with shearography and has to be measured with another technique or obtained via solving an inverse problem using for instance a realistic finite element model from which other strain tensors and elastic parameters such as stress tensors and shear modulus can be obtained. 13…”

“…This ambiguity can be tackled via the application of model-based parameter identification using, for instance, finite element modeling (FEM) as in Ref. 13. The a priori knowledge of the pressure and adjustable parameters such as the location, geometry, as well as elastic properties of surrounding soft tissue and hard tissue are used as an input parameter for the FEM.…”

“…4,5,[10][11][12] As we have shown in an earlier work, digital image correlation (DIC) combined with simulations can be used to measure elastic properties of soft materials. 13 A major disadvantage of the conventional DIC is its limitation to in-plane deformation. To obtain access to the out-of-plane component, DIC can be extended using stereo vision.…”

A quadratic optimization program for the inverse elastography problem

“…An acoustic excitation system can be used for inducing a mechanical load to the tissue leading to a deformation response. OCE combines the mechanical excitation with OCT for measuring the corresponding elastic displacement [6,10,12,14].…”