Efficient Sensitivity Based Reconstruction Technique to Accomplish Breast Hyperelastic Elastography.

Saeid Rashidi,Ali Fallah,Maryam Mehdizadeh Dastjerdi

doi:10.1155/2018/3438470

Abstract

Hyperelastic models have been acknowledged as constitutive equations which reliably model the nonlinear behaviors observed from soft tissues under various loading conditions. Among them, the Mooney-Rivlin, Yeoh, and polynomial models have been proved capable of accurately modeling responses of breast tissues to applied compressions. Hyperelastic elastography technique takes advantage of the disparities between hyperelastic parameters of varied tissues and the change in hyperelastic parameters in pathological processes. The precise reconstruction of hyperelastic parameters of a completely unknown pathology in the breast in a noninvasive and nondestructive way using the ultrasound elastography has been scrutinized in this paper. In the ultrasound elastography, tissue displacement field is extracted from radio frequency signals or images recorded using the ultrasound medical imaging system; hence the exact displacement field might not be obtained. Our results indicate that the parameters estimated by manipulating the iterative sensitivity-matrix based method converge to tissue's real hyperelastic parameters providing appropriate parameters are assigned to the hypothetical hyperelastic and regularization parameters. Iterative methods have therefore been proposed to compute proper hypothetical hyperelastic and regularization parameters. Accurate estimates of hyperelastic parameters of obscure breast pathology have been achieved even from imprecise measurements of displacements induced in the tissue by the ramp excitation.

Highlights

In the past two decades, substantial efforts have been made to bring the novel promising imaging approach “elastography” proposed by Ophir et al [1] into clinical use
Ultrasound elastography approaches, which benefit from the superiority of conventional ultrasound (US) as being a safe, easy-to-use, inexpensive, nondestructive, noninvasive, widely available, and versatile medical imaging system, have received considerable attention
(2) Shear Wave Imaging (SWI): which is capable of measuring shear wave speed, cs, in the tissue by taking the dynamic response of tissue to a mechanical vibration or acoustic radiation force into account

Summary

Introduction

In the past two decades, substantial efforts have been made to bring the novel promising imaging approach “elastography” proposed by Ophir et al [1] into clinical use. (iii) Prime elastic parameter estimation techniques involving linear elastic regime and geometrically or materially nonlinear forward model, for example, least-square based cost functionals, sensitivity based tactics, and integral approaches. With respect to the geometrically nonlinear response of soft tissues at large deformations, i.e., the nonlinearity of the strain-displacement relation, an integral approach has been proposed by Skovoroda et al [15] to reconstruct the elasticity distribution of soft tissue. The gradient-based quasi-Newton optimization method has been applied to minimize the cost function in consideration of the spatial distribution of material properties. Two iterative methods founded on the stress-strain relation and sensitivity matrix have been, respectively, applied to estimate proper hypothetical and precise real hyperelastic parameters for the unknown tissues from limited displacement quantities in the tissues. The decrease in the errors of elastic parameters estimated for the tumor, by comparing with the real elastic parameter estimated for the tumor, is the essence of the proposed iterative methods which lead to appropriate hypothetical and accurate real hyperelastic constants and suitable regularization parameter

Materials and Methods

Results and Discussion

Conclusions