Shear-Wave Elastography of the Breast: Value of a Quality Measure and Comparison with Strain Elastography

Purpose: To determine whether addition of quality measure (QM) of shear-wave (SW) velocity (V-s) estimation can increase SW elastography sensitivity for breast cancer. Materials and Methods: With written informed consent, this institutional review board-approved, HIPAA-compliant study included 143 women (mean age, 48.5 years +/- 8.7) scheduled for breast biopsy. Mean lesion size was 16.4 mm +/- 11.8; 95 (66%) lesions were benign; 48 (34%), malignant. If more than one lesion was present, lesion with highest Breast Imaging Reporting and Data System (BI-RADS) category was chosen. If there were more than one with highest BI-RADS category, a lesion was randomly selected. Conventional ultrasonography (US), strain elastography, and SW elastography were performed with QM. QM assesses SW quality to provide accurate V-s. Lesions were evaluated for V-s and QM (high or low). Lesions with V-s of less than 4.5 m/sec were classified benign; lesions with V-s of 4.5 m/sec or greater, malignant.Results were correlated with pathologic findings. V-s data with or without incorporating QM were used to determine SW elastography diagnostic performance. Binomial proportions and exact 95% confidence intervals (CIs) were calculated. Results: In 95 benign lesions, 13 (14%) had no SW elastography signal; 77 (81%), V-s of less than 4.5 m/sec; and five (5%), V-s of 4.5 m/sec or greater. In 48 malignant lesions, eight (17%) had no SW elastography signal; 20 (42%), V-s of less than 4.5 m/sec; and 20 (42%), V-s of 4.5 m/sec or greater. QM was low in 17 of 20 (85%) malignant lesions with V-s of less than 4.5 m/sec. Without QM, using V-s of 4.5 m/sec or greater as test positive, SW elastography had lesion-level sensitivity of 50% (95% CI: 34%, 66%); specificity, 94% (95% CI: 86%, 98%); positive predictive value (PPV), 80% (95% CI: 59%, 93%); and negative predictive value (NPV), 79% (95% CI: 70%, 87%). Using QM where additional lesions with both low V-s and low QM were treated as test positive, SW elastography had lesion-level sensitivity of 93% (95% CI: 80%, 98%); specificity, 89% (95% CI: 80%, 95%); PPV, 80% (95% CI: 66%, 91%); and NPV, 96% (95% CI: 89%, 99%). Conclusion: Addition of QM can improve SW elastography sensitivity, with no significant change in specificity. (C) RSNA, 2014