Shear wave elastography for solid breast masses evaluation: Quantitative measurement of mean elasticity value and elasticity ratio

Abstract

Purpose: Shear wave elastography (SWE), an ultrasonographic technique to measure the elasticity of mass lesions to evaluate breast mass. This study aimed to find out the cutoff values identifying breast malignancy using the mean elasticity (E-mean) and elasticity ratio (E-ratio) of breast masses.

Methods: This retrospective study included women underwent SWE and US-guided biopsy of breast masses. During conventional US, the SWE mode was also performed, determining elasticity measurements, E-mean and E-ratio. Histopathological reports were obtained to identify mass status. The optimal and alternative cutoff values for E-mean and E-ratio to determine malignancy were assessed by receiver operating characteristic (ROC) curve analysis and Youden's index score.

Results: Among 147 benign and 93 malignant masses, the median of E-means were 26.20 (IQR 15.70-56.60) and 141.60 (IQR 119.80-154.60) kPa and the median E-ratios were 3.11 (IQR 1.83-5.23) and 9.24 (IQR 6.76-12.44), respectively. Using Youden's index, the optimal cutoff values for E-mean and E-ratio were 90.35 and 5.89, with sensitivity of 87.1 % and 82.8 %, specificity of 89.1 % and 83.7 %, positive predictive value (PPV) of 83.5 % and 76.2 %, negative predictive value (NPV) of 91.6 % and 88.5 %, positive likelihood ratio (LR+) of 8.00 and 5.07, and negative likelihood ratio (LR-) of 0.14 and 0.21, respectively.

Conclusion: This study revealed that SWE is useful in predicting malignancy. With the optimal cutoff values of E-mean and E-ratio at 90.35 kPa and 5.89, the sensitivity was nearly 90 % with E-mean and slightly over 80 % with E-ratio, respectively. These findings could be used in conjunction with conventional US.

Keywords: Breast mass; Elasticity ratio; Mean elasticity; Shear wave elastography; Ultrasound.

Fig. 1

Fig. 1A. Shear wave elastography and grayscale ultrasound image of a 20 mm fibroadenoma. The shear wave image shows the lesion in homogeneous blue, defined the most stiffness site as inside tumor. The E-mean and E-ratio are 21.2 kPa and 3.55. Fig. 1B. A 7 mm invasive ductal carcinoma with homogeneous blue. The E-mean and E-ratio are 35.9 kPa and 2.25. Fig.1C. A 22 mm invasive ductal carcinoma. The shear wave image shows the mass and surrounding tissue in heterogeneous color and the zone of stiffness is irregular in red, yellow, and green color. The most stiffness site is red and inside tumor. The E-mean and E-ratio are 167.5 kPa and 13.07. Fig. 1D. A 11 mm invasive ductal carcinoma defined the most stiffness site as peritumoral site. The E-mean and E-ratio are 144.1 kPa and 10.32.

Fig. 2

ROC Curve of E-mean and E-ratio to determine malignancy status of breast masses. Cutoff value for average E-mean at 90.35 kPa (A; sensitivity 0.871 and specificity 0.891), while cutoff value for average E-ratio at 5.89 (B; sensitivity 0.828 and specificity 0.837).