Purpose: To evaluate the performance of shear wave elastography (SWE) for the differentiation of sonographically detected breast masses and correlate elasticity values and American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) assessments with pathologic findings.
Materials and Methods: Between March 2010 and May 2010, conventional US and SWE were performed by three experienced radiologists for 208 breast in 172 consecutive women who had been scheduled for USguided core biopsy or surgical excision. Among those patients there were mammographically negative, sonographically detected 64 lesions in 55 asymptomatic patients. Receiver operating characteristic (ROC) curves for the B-mode US and SWE images were analyzed to evaluate diagnostic performance and to compare the performance of established BI-RADS categories and elasticity values in terms of the Young’s modulus (in kilopascals, kPa). The optimal cut-off values for B-mode and SWE, yielding the maximal sum of sensitivity and specificity, were calculated. The sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) using the cut-off values were measured. Results were correlated with pathologic
findings.
Results: The mean elasticity values were significantly higher in malignant masses (151.9 kPa ± 26.7) than in benign masses (47.3 kPa ± 41.2), (p <0.0001) on SWE. The area under ROC values were 0.934 (95% confidence interval: 0.842, 0.81 for conventional US and 0.952 (95% confidence interval: 0.842, 0.981) for SWE, which was not significantly different (p = 0.83). Optimal cut-off value, yielding the maximal sum of sensitivity and specificity, was category 4B with conventional B-mode US, and 103 kPa with SWE. The sensitivity and specificity of conventional US were 85.7% (6/7) and 96.5% (55/57), and for SWE, 100% (7/ 7) and 91.2% (52/ 57). Positive predictive values and negative predictive values were 75% (6/8) and
98.2 % (55/56) for conventional B-mode with cutoff point of BI-RADS category 4B, whereas PPV and NPV for SWE were 58.3% (7/12) and 100% (52/52). Of the biopsy-proven 46 BI-RADS 4A lesions, 89.1% (41/ 46) had elasticity value less than 100 kPa and there was no malignant lesion.
Conclusion: There were significant differences in the elasticity values of benign and malignant masses for sonographically
detected masses. Sonographically detected BI-RADS category 4a lesions with lower than 100 kPa values on SWE do not require biopsy.
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