Application of 3D and 2D quantitative shear wave elastography (SWE) to differentiate between benign and malignant breast masses

Abstract

As breast cancer tissues are stiffer than normal tissues, shear wave elastography (SWE) can locally quantify tissue stiffness and provide histological information. Moreover, tissue stiffness can be observed on three-dimensional (3D) colour-coded elasticity maps. Our objective was to evaluate the diagnostic performances of quantitative features in differentiating breast masses by two-dimensional (2D) and 3D SWE. Two hundred ten consecutive women with 210 breast masses were examined with B-mode ultrasound (US) and SWE. Quantitative features of 3D and 2D SWE were assessed, including elastic modulus standard deviation (E_SD^E) measured on SWE mode images and E_SD^U measured on B-mode images, as well as maximum elasticity (E_max). Adding quantitative features to B-mode US improved the diagnostic performance (p < 0.05) and reduced false-positive biopsies (p < 0.0001). The area under the receiver operating characteristic curve (AUC) of 3D SWE was similar to that of 2D SWE for E_SD^E (p = 0.026) and E_SD^U (p = 0.159) but inferior to that of 2D SWE for E_max (p = 0.002). Compared with E_SD^U, E_SD^E showed a higher AUC on 2D (p = 0.0038) and 3D SWE (p = 0.0057). Our study indicates that quantitative features of 3D and 2D SWE can significantly improve the diagnostic performance of B-mode US, especially 3D SWE E_SD^E, which shows considerable clinical value.

Figure 1. Invasive ductal carcinoma grade 2 in a 61-year-old woman.

The 2D B-mode image shows an irregular hypoechoic mass considered to be BI-RADS category 4b (bottom). On 2D SWE (a) and 3D SWE (b), an ROI for measuring the E_SD^E value was placed to include the whole breast mass and immediately adjacent stiff tissue. The other Q-Box for measuring the E_SD^U was placed within the mass to encompass the maximum portion of the mass and exclude tissue outside the mass. (a) E_max value recorded using the larger Q-Box. (b) E_max value recorded using a 2-mm² Q-Box (arrow).

Figure 2. Fibroadenoma in a 45-year-old woman.

(a) The 2D B-mode image shows a hypoechoic mass with parallel orientation considered to be BI-RADS category 4a (bottom). Both 2D SWE (a) and 3D SWE (b) show a homogeneously soft (blue colour) mass and surrounding tissue (2D E_max 47.6 kPa, E_SD^E 8.0 kPa, E_SD^U 7.7 kPa; 3D E_max 54.6 kPa, E_SD^E 10.8 kPa, E_SD^U 9.1 kPa). When combining SWE and B-mode US, BI-RADS category 3 was assigned to the mass.

Figure 3. Fibroadenoma in a 29-year-old woman.

(a) The 2D SWE shows a homogeneously soft (blue colour) mass and surrounding tissue at the margin of the breast mass (E_max 49.7 kPa). (b) Multi-slice 3D SWE images show a heterogeneously stiff mass with scattered red colour (arrow) (E_max 155 kPa).

Figure 4. DCIS in a 36-year-old woman.

(a) The 2D B-mode image shows a 7.4-mm, irregular hypoechoic mass with an uncircumscribed margin considered to be BI-RADS category 4a. Both 2D SWE (b) and 3D SWE (c) show a homogeneously soft (blue colour) mass and surrounding tissue (2D E_max 58.7 kPa, E_SD^E 10.2 kPa, E_SD^U 9.4 kPa; 3D E_max 87.1 kPa, E_SD^E 11.8 kPa, E_SD^U 9.5 kPa). When combining SWE with B-mode US, BI-RADS category 3 was assigned to the mass.