Journal List > J Korean Soc Radiol > v.81(1) > 1141988

Lee, Kim, Lee, Kim, and Yoon: Application of Point Shearwave Elastography to Breast Ultrasonography: Initial Experience Using “S-Shearwave” in Differential Diagnosis

Abstract

Purpose

To evaluate the optimal measurement location, cut-off value, and diagnostic performance of S-Shearwave in differential diagnosis of breast masses seen on ultrasonography (US).

Materials and Methods

During the study period, 225 breast masses in 197 women were includ-ed. S-Shearwave measurements were made by applying a square region-of-interest automati-cally generated by the US machine. Shearwave elasticity was measured three times at four different locations of the mass, and the highest shearwave elasticity was used for calculating the optimal cut-off value. Diagnostic performance was evaluated by using the area under the receiv-ing operator characteristic curve (AUC).

Results

Of the 225 breast masses, 156 (69.3%) were benign and 69 (30.7%) were malignant. Mean S-Shearwave values were significantly higher for malignant masses (108.0 ± 70.0 kPa vs. 43.4 ± 38.3 kPa;p < 0.001). No significant differences were seen among AUC values at different measurement locations. With a cut-off value of 41.9 kPa, S-Shearwave showed 85.7% sensitivity, 63.9% specificity, 70.7% accuracy, and positive and negative predictive values of 51.7% and 90.8%, respectively. The AUCs for US and S-Shearwave did not show significant differences (p = 0.179).

Conclusion

S-Shearwave shows comparable diagnostic performance to that of grayscale US that can be applied for differential diagnosis of breast masses seen on US.

Index terms

Breast, Ultrasonography, Neoplasm, Elasticity Imaging Techniques

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Fig. 1.
Example of application of S-Shearwave to breast ultrasonography examination. A. A square ROI is set at the center of the breast mass for shearwave elasticity measurement. B. An ROI is set at the normal breast parenchyma adjacent to the breast mass, with the ROI set at the same depth as that of the breast mass.
jksr-81-157f1.tif
Fig. 2.
After generating the S-Shearwave, shearwave elasticity is measured three times at four different locations of the mass by applying square regions-of-interest – interior (mass center), superior border, right lateral border, and left lateral border of the mass.
jksr-81-157f2.tif
Table 1.
Comparison of Mean S-Shearwave Values between Breast Masses
  Benign (n = 156) Malignancy (n = 69) p
Mass Parenchyma p Mass Parenchyma p
Mass center 29.0 ± 30.0 18.3 ± 15.3 < 0.001 72.0 ± 67.4 13.1 ± 9.2 < 0.001 < 0.001
Superior margin 33.9 ± 77.8 18.3 ± 15.3 < 0.001 77.6 ± 58.1 13.1 ± 9.2 < 0.001 < 0.001
Right lateral margin 26.8 ± 26.8 18.3 ± 15.3 < 0.001 52.0 ± 47.4 13.1 ± 9.2 < 0.001 < 0.001
Left lateral margin 27.2 ± 27.7 18.3 ± 15.3 < 0.001 53.4 ± 41.5 13.1 ± 9.2 < 0.001 < 0.001

Data are displayed as mean ± standard deviation (kPa).

Comparison of mean elasticity values between benign masses and surrounding parenchyma.

Comparison of mean elasticity values between benign and malignant masses in the four measurement locations.

Table 2.
Diagnostic Performance of S-Shearwave According to Measurement Location
  Mass Center Superior Margin Right Lateral Margin Left Lateral Margin Overall p
Cut-off level (kPa) > 25.8 > 32.2 > 24.1 > 29.5 -
Sensitivity 80.0 (70.6–89.4) 82.9 (74.0–91.7) 68.6 (57.7–79.5) 70.0 (59.3–80.7) 0.024
Specificity 63.2 (55.6–70.8) 63.9 (56.3–71.4) 70.3 (63.1–77.5) 74.2 (67.3–81.1) 0.014
PPV 49.6 (40.3–58.8) 50.9 (41.7–60.1) 51.1 (41.0–61.2) 55.1 (44.7–65.4) 0.521
NPV 87.5 (81.4–93.6) 89.2 (83.4–95.0) 83.2 (76.8–89.6) 84.6 (78.5–90.6) 0.189
Accuracy 68.4 (62.4–74.5) 69.8 (68.8–75.8) 69.8 (63.8–75.8) 72.9 (67.1–78.7) 0.586
AUC 0.716 (0.656–0.777) 0.734 (0.675–0.792) ) 0.695 (0.629–0.760) 0.721 (0.657–0.785) > 0.999

95% confidence intervals are in parentheses.

Cut-off level is calculated by Youden's index with the maximum S-Shearwave elasticity among the median values calculated from the three elasticity measurements obtained from each location.

AUC = area under the receiver operator characteristics curve, NPV = negative predictive value, PPV = positive predictive value

Table 3.
Diagnostic Performance of S-Shearwave and US for the 225 Breast Masses
  S-Shearwave US Alone p
Sensitivity 85.7 (77.5–93.9) 98.6 (96,2–100.0) 0.002
Specificity 63.9 (56.3–71.4) 58.3 (51.0–66.5) 0.332
PPV 51.7 (42.6–60.8) 51.1 (43.8–60.7) 0.888
NPV 90.8 (85.4–96.2) 98.9 (96.2–100.0) 0.002
NPV Accuracy 90.8 (85.4–96.2)70.7 (64.7–76.6) 98.9 (96.2–100.0) 70.7 (65.7–77.5) 0.002 0.821
AUC 0.748 (0.692–0.804) 0.794 (0.755–0.832) 0.179

95% confidence intervals are in parentheses.

Cut-off level of S-Shearwave in general is used as 41.9 kPa.

AUC = area under the receiver operator characteristics curve, NPV = negative predictive value, PPV = positive predictive value, US = ultrasonograpy

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