Elastic nonlinearity imaging

Abstract

Previous work has demonstrated improved diagnostic performance of highly trained breast radiologists when provided with B-mode plus elastography images over B-mode images alone. In those studies we have observed that elasticity imaging can be difficult to perform if there is substantial motion of tissue out of the image plane. So we are extending our methods to 3D/4D elasticity imaging with 2D arrays. Further, we have also documented the fact that some breast tumors change contrast with increasing deformation and those observations are consistent with in vitro tissue measurements. Hence, we are investigating imaging tissue stress-strain nonlinearity. These studies will require relatively large tissue deformations (e.g., > 20%) which will induce out of plane motion further justifying 3D/4D motion tracking. To further enhance our efforts, we have begun testing the ability to perform modulus reconstructions (absolute elastic parameter) imaging of in vivo breast tissues. The reconstructions are based on high quality 2D displacement estimates from strain imaging. Piecewise linear (secant) modulus reconstructions demonstrate the changes in elasticity image contrast seen in strain images but, unlike the strain images, the contrast in the modulus images approximates the absolute modulus contrast. Nonlinear reconstructions assume a reasonable approximation to the underlying constitutive relations for the tissue and provide images of the (near) zero-strain shear modulus and a nonlinearity parameter that describes the rate of tissue stiffening with increased deformation. Limited data from clinical trials are consistent with in vitro measurements of elastic properties of tissue samples and suggest that the nonlinearity of invasive ductal carcinoma exceeds that of fibroadenoma and might be useful for improving diagnostic specificity. This work is being extended to 3D.

Relative Elastic Modulus Imaging Using Sector Ultrasound Data for Abdominal Applications: An Evaluation of Strategies and Feasibility

“…However, because the absolute force information cannot be obtained using conventional ultrasound equipment, only relative modulus information can be obtained through the above-mentioned reconstruction process. REMI has recently been extended to assess tissue nonlinearity in breast tissues [13, 14]. Positive outcomes have also been achieved when the REMI technique was applied to age assessment of DVT [15], differentiation of breast lesions [13, 14], monitoring thermal ablation therapies [12, 16] and detection of prostate cancer [17].…”

A Normalized Shear Deformation Indicator for Ultrasound Strain Elastography in Breast Tissues: An In Vivo Feasibility Study

“…Several factors could potentially confound local shear deformation. In addition to the nonlinear elasticity [ 32 ], the slipping boundary in the tumor-background interface could be another confounding factor because it could cause high NSDI values around the tumor boundary (see Figure 2(b) ). Tissue-dependent viscosity could also play a role in the change of strain contrast, thereby affecting the shear deformation.…”

Automated palpation for breast tissue discrimination based on viscoelastic biomechanical properties

“…Since the 2000s, this focus has shifted to parameters that express the nonlinear material behavior of biological tissues, such as nonlinear elasticity, hyperelasticity and viscoelasticity. Some researchers [6], including Hall et al [7] and Mehrabian et al [8,9], have applied ultrasound and finite element inverse analysis to determine the elastic nonlinearity under large strains (around 10 % axial strain). Additionally, many researchers have reported dynamic multifrequency elastography for viscoelastic imaging using MRI and external oscillation devices [10][11][12].…”