Recent Results in Nonlinear Strain and Modulus Imaging

Abstract

We report a summary of recent developments and current status of our team’s efforts to image and quantify in vivo nonlinear strain and tissue mechanical properties. Our work is guided by a focus on applications to cancer diagnosis and treatment using clinical ultrasound imaging and quasi-static tissue deformations. We review our recent developments in displacement estimation from ultrasound image sequences. We discuss cross correlation approaches, regularized optimization approaches, guided search methods, multiscale methods, and hybrid methods. Current implementations can return results of high accuracy in both axial and lateral directions at several frames per second. We compare several strain estimators. Again we see a benefit from a regularized optimization approach. We then discuss both direct and iterative methods to reconstruct tissue mechanical property distributions from measured strain and displacement fields. We review the formulation, discretization, and algorithmic considerations that come into play when attempting to infer linear and nonlinear elastic properties from strain and displacement measurements. Finally we illustrate our progress with example applications in breast disease diagnosis and tumor ablation monitoring. Our current status shows that we have demonstrated quantitative determination of nonlinear parameters in phantoms and in vivo, in the context of 2D models and data. We look forward to incorporating 3D data from 2D transducer arrays to noninvasively create calibrated 3D quantitative maps of nonlinear elastic properties of breast tissues in vivo.

Strain estimation by a Fourier Series-based extrema tracking algorithm for elastography

“…E rms defined in Eq. (19) can be regarded as the quantitative form of the real-versus-estimated strain error (RESE). E rms s of the three algorithms are provided in Figure 11(b).…”

“…To resolve such a problem, smoothing techniques (e.g., the median filtering 40 technique) are often applied to the displacement field before the gradient operation to remove shot or false peak noises. Regularized elastography methods [19,20] can also be employed to eliminate large displacement estimation errors due to false correlation peaks and to assure smooth strain calculation from the noisy displacement estimation.…”

A GPU-Accelerated 3-D Coupled Subsample Estimation Algorithm for Volumetric Breast Strain Elastography

“…Ultrasound SE has shown promise in differentiating breast tumors [2], [3]. Recent advancements in SE can be found in recent review articles [4], [5]. The potential of elastography has resulted in several major vendors ( e.g.…”

Design and Testing of a Single-Element Ultrasound Viscoelastography System for Point-of-Care Edema Quantification

“…Biological tissues however are rarely linearly elastic. They can more accurately be described using more complex poroelastic (Armstrong et al 1984), viscoelastic (Fung 1993), or nonlinear elasticity models (Hall et al 2011). Elastography techniques aimed at measuring these types of properties generally fall into three groups based on the material model: poroelastography, viscoelastography, and nonlinear elastography.…”