Ultrasonic Viscoelasticity Imaging of Nonpalpable Breast Tumors

Abstract

Rationale and Objectives Improvements in the diagnosis of early breast cancers depend on a physician’s ability to obtain the information necessary to distinguish nonpalpable malignant and benign tumors. Viscoelastic features that describe mechanical properties of tissues may help to distinguish these types of lesions. Materials and Methods 21 patients with nonpalpable, pathology-confirmed BI-RADS 4 or 5 breast lesions (10 benign, 11 malignant) detected by mammography were studied. Viscoelastic parameters were extracted from a time sequence of ultrasonic strain images and differences in the parameters between malignant and benign tumors were compared. Parametric data were color coded and superimposed on sonograms. Results The strain retardance time parameter, T1, provided the best discrimination between malignant and benign tumors (p<0.01). T1 measures the time required for tissues to fully deform (strain) once compressed, and therefore it describes the time-varying viscous response of tissue to a small deforming force. Compared to the surrounding background tissues, malignant lesions have smaller average T1 values while benign lesions have larger T1 values. This tissue-specific contrast correlates with known changes in the extracellular matrix of breast stroma. Conclusion Characterization of nonpalpable breast lesions is improved by the addition of viscoelastic strain imaging parameters. The differentiation of malignant and benign BI-RADS 4 or 5 tumors is especially evident with the use of the retardation time estimates, T1.

Material properties from acoustic radiation force step response

“…10 Classification of nonpalpable, isoelastic lesions is possible by imaging time-varying strain features. 6,7 Despite early clinical successes, the visibility of lesions in elasticity imaging can vary widely. We hypothesize that some of the clinical variability may be reduced by improving our understanding of elasticity imaging contrast mechanisms and adapting the imaging techniques accordingly.…”

“…[1][2][3][4][5][6][7] Its diagnostic value stems from the important role of the cellular mechanoenvironment in regulating tumor growth 8 and from the large tumor contrast observed for various mechanical properties. 9 Biological sources of elastic strain contrast in mammary tissues include edema, hyperplasia, acidosis, fibrosis, desmoplasia, and inflammatory responses characteristic of the reaction of breast stroma to cancer cells.…”

Building a virtual simulation platform for quasistatic breast ultrasound elastography using open source software: A preliminary investigation

“…From a time series of RF echo frames simulated during the simulation of time-dependent strain imaging, 35 strain images were first estimated through speckle tracking. Then, one time-resolved strain curve for each and every pixel was obtained as shown in Fig.…”

“…4. Each time-resolved strain curve was fitted into a Kevin-Voigt model 35 using the Optimization Toolbox in  (Mathworks, Inc., MA). The formula of strain creep under the Kevin-Voigt model is provided below…”

“…As shown in Table I, three bio-mechanical simulations were performed to mimic three different QUE applications, namely, small deformation strain imaging, 10 nonlinear strain imaging, 33,34 and time-dependent strain imaging. 35 In FE simulations, the elasticity of breast tissues was simulated by the Veronda-Westmann (V-W) hyperelastic model. 36 T I. Descriptions of FE-simulations related to three QUE applications.…”