Korean J Radiol.  2020 Apr;21(4):431-441. 10.3348/kjr.2019.0479.

Comparison of One- and Two-Region of Interest Strain Elastography Measurements in the Differential Diagnosis of Breast Masses

• Park HJ
• Kim SM
• Yun BL
• Jang M
• Kim B
• Lee SH
• Ahn HS

• KMID: 2471809
• DOI: http://doi.org/10.3348/kjr.2019.0479

Abstract

OBJECTIVE
To compare the diagnostic performance and interobserver variability of strain ratio obtained from one or two regions of interest (ROI) on breast elastography.
MATERIALS AND METHODS
From April to May 2016, 140 breast masses in 140 patients who underwent conventional ultrasonography (US) with strain elastography followed by US-guided biopsy were evaluated. Three experienced breast radiologists reviewed recorded US and elastography images, measured strain ratios, and categorized them according to the American College of Radiology breast imaging reporting and data system lexicon. Strain ratio was obtained using the 1-ROI method (one ROI drawn on the target mass), and the 2-ROI method (one ROI in the target mass and another in reference fat tissue). The diagnostic performance of the three radiologists among datasets and optimal cut-off values for strain ratios were evaluated. Interobserver variability of strain ratio for each ROI method was assessed using intraclass correlation coefficient values, Bland-Altman plots, and coefficients of variation.
RESULTS
Compared to US alone, US combined with the strain ratio measured using either ROI method significantly improved specificity, positive predictive value, accuracy, and area under the receiver operating characteristic curve (AUC) (all p values < 0.05). Strain ratio obtained using the 1-ROI method showed higher interobserver agreement between the three radiologists without a significant difference in AUC for differentiating breast cancer when the optimal strain ratio cut-off value was used, compared with the 2-ROI method (AUC: 0.788 vs. 0.783, 0.693 vs. 0.715, and 0.691 vs. 0.686, respectively, all p values > 0.05).
CONCLUSION
Strain ratios obtained using the 1-ROI method showed higher interobserver agreement without a significant difference in AUC, compared to those obtained using the 2-ROI method. Considering that the 1-ROI method can reduce performers' efforts, it could have an important role in improving the diagnostic performance of breast US by enabling consistent management of breast lesions.

Keyword

Breast; Elastography; Region of interest; Strain ratio

MeSH Terms

Area Under Curve
Biopsy
Breast Neoplasms
Breast*
Dataset
Diagnosis, Differential*
Elasticity Imaging Techniques*
Humans
Information Systems
Methods
Observer Variation
ROC Curve
Sensitivity and Specificity
Ultrasonography

Figure

• 

  Fig. 1 Representative images showing ROI used to obtain strain ratio using 1-ROI (A) and 2-ROI methods (B).A. For 1-ROI method, oval ROI was set to include mass (green circle) in which US unit automatically calculated and visualized strain ratio as mean strain within ROI drawn along border of mass divided by mean strain of fat located at and above level of ROI set for mass strain measurement, excluding strain measured within ROI set for mass measurement (yellow box). B. For 2-ROI method, one ROI was drawn along border of targeted breast mass (green circle) and another was drawn in lateral subcutaneous fat tissue located near target lesion (orange circle). Reference strain for 2-ROI method (B) was measured as average strain within orange circle. ROI = region of interest, US = ultrasonography

• 

  Fig. 2 27-year-old woman diagnosed with fibroadenoma on US-guided biopsy was stable during > 2 years of follow-up.A. Transverse B-mode US image shows 9-mm indistinct oval hypoechoic mass (arrows) in left breast that was categorized as Category 4a by each radiologist. B. Strain elastography showed that mass had some hard areas (arrows). Strain ratios using 1-ROI method were 2.25 (C), 2.16 (D), and 2.17 (E) according to three radiologists (green circle indicated ROI for target lesion). Strain ratios using 2-ROI method were 2.80 (F), 2.26 (G), and 3.54 (H) according to three radiologists (green circle indicated ROI for target lesion, orange circle indicated ROI for reference fat).

• 

  Fig. 3 Series of Bland-Altman plots show interobserver agreement of strain ratios for both 1-ROI (A–C) and 2-ROI methods (D–F).Each dot represents difference in strain ratios between two radiologists measured using same ROI method for each of 140 breast masses. Middle horizontal line represents mean difference in strain ratio, and each line above and below horizontal line represents mean difference between upper and lower limits of 95% agreement limit. For 1-ROI method, mean differences in strain ratios were as follows: (A) 0.891, with upper and lower limits of 3.533 and −1.751 between radiologists 1 and 2; (B) 0.746 with upper and lower limits of 3.599 and −2.108 between radiologists 1 and 3; and (C) −0.145 with upper and lower limits of 1.712 and −2.003 between radiologists 2 and 3. For 2-ROI method, mean differences in strain ratios were as follows: (D) 3.251, with upper and lower limits of 10.228 and −3.726 between radiologists 1 and 2; (E) 2.431 with upper and lower limits of 9.213 and −4.350, between radiologists 1 and 3; and (F) −0.820, with upper and lower limits of 2.106 and −3.746 between radiologists 2 and 3. SD = standard deviation

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