Rationale and Objectives
The aim of this study was to evaluate and compare the diagnostic performance of elastography, B-mode ultrasound (US), and a combination of elastography and B-mode US for the differentiation of small breast masses.
Materials and Methods
A total of 315 breast masses < 1 cm (267 benign, 48 malignant) in 278 patients were examined with B-mode US and elastography. Histopathologic results were used as a reference standard. Two radiologists retrospectively evaluated the B-mode images according to the American College of Radiology Breast Imaging Reporting and Data System and elastographic images according to the elasticity scoring classification system proposed by Itoh et al and the strain ratio. B-mode US and elastography were combined according to the cutoff value. The diagnostic performance of B-mode US, elastography, and the combination of the two modalities was compared using receiver-operating characteristic curve analysis.
Results
The mean elasticity score for malignant masses (3.02 ± 1.33) was significantly higher than that for benign masses (1.72 ± 0.78) ( P < .001). Areas under the receiver-operating characteristic curves were 0.616 for B-mode US, 0.784 for elasticity score, 0.668 for strain ratio, 0.727 for the combination of B-mode US and elasticity score, and 0.701 for the combination of B-mode US, elasticity score, and strain ratio. The sensitivity, specificity, positive predictive value, and negative predictive value were 93.8%, 51.7%, 25.9%, and 97.9%, respectively, when elasticity score and B-mode US were combined as follows: downgrade of B-mode US assessment category in cases with elasticity scores of 1, no change in cases with scores of 2 or 3, and upgrade in cases with scores of 4 or 5.
Conclusion
Elasticity score alone showed the best diagnostic performance, but a combination of B-mode US and elasticity score may have predictive value for the differentiation of benign and malignant lesions <1 cm.
Elastography is a method of visualizing the elasticity characteristics of a lesion. Several clinical studies have reported that elastography has the potential to differentiate benign from malignant solid breast masses and have shown similar or inferior diagnostic performance compared with conventional B-mode ultrasound (US), with sensitivity of 65% to 100% and specificity of 32% to 98.5% . The interpretation criteria in elastography consist of the qualitative parameter of elasticity score and the quantitative parameter of strain ratio . Most studies have compared the diagnostic performance of the elasticity score and the strain ratio with B-mode US, and studies of the diagnostic performance of the combination of B-mode US and elastography are rare . In such studies, on the basis of the subjective determinations of the investigators, final assessments were performed by combining the two modalities, and the results were reported not to be better than using B-mode US alone.
If the size of a mass is small, it is difficult to analyze according to the Breast Imaging Reporting and Data System, and the characterization of the lesion may not be accurate. Therefore, we evaluated the diagnostic performance of elastography for differentiation between benign and malignant small breast masses. We also compared the diagnostic performance of elastography alone, B-mode US alone, and the combination of the two modalities.
Materials and methods
Patients
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Pathologic Analysis
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Image Acquisition and Analysis
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Statistical Analysis
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Results
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Table 1
Comparison of the Diagnostic Performance of B-mode US Alone, Elastography Alone, and the Combination of the Two Modalities
B-mode US Elastography Combination of B-mode US and Elastography BI-RADS Category Elasticity Score Strain Ratio BS Method BR Method BSR Method Sensitivity 95.8% 93.8% 68.8% 93.8% 97.9% 93.8% Specificity 27.3% 45.7% 64.8% 51.7% 21.4% 46.4% PPV 19.2% 23.7% 26% 25.9% 18.3% 23.9% NPV 97.3% 97.6% 92% 97.9% 98.3% 97.6% Az (95% CI) 0.616 (0.560–0.670 0.784 (0.735–0.828) 0.668 (0.613–0.720) 0.727 (0.674–0.776) 0.596 (0.540–0.651) 0.701 (0.647–0.751)
Az, area under the receiver-operating characteristic curve; BI-RADS, Breast Imaging Reporting and Data System; BR, combination of B-mode ultrasound and strain ratio; BS, combination of B-mode ultrasound and elasticity score; BSR, combination of B-mode ultrasound, elasticity score, and strain ratio; CI, confidence interval; NPV, negative predictive value; PPV, positive predictive value; US, ultrasound.
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Conventional B-mode US
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Elastography: Elasticity Score and Strain Ratio
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Combination of B-mode US and Elastography
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Discussion
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Conclusions
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