Please Explain the Basic Concept of Ultrasound Elastography, and How Can It Help Differentiate Benign From Malignant Breast Lesions?

Abstract

the strain source and then visualizes the strain induced in tissue with the use of either an external or internal source. In harmonic elastography, low-frequency acoustic waves are transmitted within the tissue. The phase and amplitude of the propagating waves are visualized using color Doppler imaging [3, 4]. In transient elastography, an ultrasound scanner with a high frame rate (i.e., 10,000 frames per second) is used to generate and then track the propagation of shear waves in tissue [5]. Shear waves are tissue movements perpendicular to the direction of the ultrasound wave transmission. In terms of breast elastography, malignant masses tend to be more irregular, are heterogeneous, and typically appear larger at elastography than at gray-scale imaging [6, 7]. In terms of quantitative analysis, malignant lesions generally also exhibit maximum stiffness greater than 80–100 kPa [7, 8]. Invasive cancers with a high histologic grade, large tumor size, nodal involvement, and vascular invasion have also been shown to be signifi cantly correlated with high mean stiffness at shear-wave elastography. Elastography may be useful in improving the specificity of ultrasound evaluation of BI-RADS categories 3 and 4A lesions, including complicated cysts, by avoiding unnecessary biopsy of BI-RADS category 4A masses (i.e., masses for which suspicion of malignancy was low) without a significant loss in sensitivity. Several classification systems in volving elastography, most of which are based on the color pattern, have been proposed. For example, a bull’s-eye artifact has also been described as a characteristic of benign breast cysts, which may appear as a round or oval lesion with a stiff rim associated with two soft spots, one located centrally and the other posteriorly. Ultrasound elastographic features