Original ContributionA Set of Shear Wave Elastography Quantitative Parameters Combined with Ultrasound BI-RADS to Assess Benign and Malignant Breast Lesions
Introduction
Ultrasonography (US) is a widely used tool for assessing the malignant potential of breast lesions. Ultrasound is used for breast cancer screening in China. The Breast Imaging Reporting and Data System (BI-RADS) for ultrasound provides standardized terminology to describe features, assessments and recommendations for breast lesions visible on US (American College of Radiology 2003). In BI-RADS, breast lesions are classified into categories 0 to 6, with increasing likelihood of malignancy. Studies indicate that BI-RADS is very sensitive but not specific enough to distinguish between benign and malignant lesions (Costantini et al., 2007, Kim et al., 2008, Kwak et al., 2006, Raza et al., 2008).
Breast elastography is a method for measuring tissue stiffness. The elasticity imaging concept was proposed for the first time in 1991 (Ophir et al. 1991). It has been proven to be very efficient in the evaluation of benign and malignant breast lesions (Barr et al., 2012, Itoh et al., 2006). The recently developed shear wave elastography (SWE) technique uses the acoustic radiation force induced by the ultrasound beam itself. This force induces shear waves that propagate transversely in tissue. The velocity of the shear waves is dependent on tissue elasticity. By measuring the different velocities and displaying the data using a color scale, SWE is able to provide quantitative elastic information expressed as the Young's modulus in real time. Quantitative elasticity values such as the maximum (Emax), mean (Emean), standard deviation (SD) and ratio of Emean of a lesion to Emean of surrounding parenchyma (Eratio) have proven to be useful parameters in several studies (Athanasiou et al., 2010, Chang et al., 2011, Cosgrove et al., 2012, Evans et al., 2010, Tanter et al., 2008, Wang et al., 2013).
Furthermore, several studies have reported the performance of combinations of BI-RADS and SWE features in the assessment of breast lesions (Berg et al., 2012, Chang et al., 2011, Evans et al., 2012, Youk et al., 2013). These studies reported that the combinations were helpful in assessing breast lesions, but used different SWE quantitative parameters. Chang et al. (2011) and Evans et al. (2012) reported on the combination of conventional US and Emean, Berg et al. (2012) on the combination of Emax and BI-RADS feature analysis, and Youk et al. (2013) on the combination of Eratio and BI-RADS. According to these articles, several SWE quantitative parameters, combined with ultrasound BI-RADS criteria, were valuable in assessing the malignant potential of breast lesions. Clinically, however, the optimal combination of SWE parameters for use by sonographers has not been elucidated. In this study, we evaluated different combinations of SWE parameters and concluded that using a set of all four parameters, where the positivity of any one parameter counted as a “positive” examination result, serially interpreted with ultrasound BI-RADS, had the highest sensitivity and specificity.
Section snippets
Patients and lesions
From March 2011 to September 2013, 251 consecutive patients in whom breast lesions were found on screening ultrasound or palpation underwent SWE before US-guided core needle biopsy, vacuum-assisted biopsy or surgical excision. Patients who were pregnant or lactating, had breast implants, had a scar adjacent to the lesion in question, were receiving radiotherapy or chemotherapy for cancer or had already undergone needle biopsy before the ultrasound were not included in this study. The enrolled
Results
According to BI-RADS, 114 lesions were classified as category 3, 79 lesions were classified as category 4 and 86 lesions were classified as category 5. Of the 279 lesions, 150 (53.8%) were benign and 129 (46.2%) were malignant. Benign lesions included fibroadenoma (n = 96), adenosis (n = 35), adenoma (n = 7) and papilloma (n = 12). Malignant lesions included invasive ductal carcinoma (n = 120), invasive lobular carcinoma (n = 2), ductal carcinoma in situ (n = 5), lobular carcinoma in situ
Discussion
Emax, Emean, SD and Eratio all performed well when assessed individually. Compared with BI-RADS, the four parameters had lower sensitivity and higher specificity. We hypothesized that together, the four parameters had the potential to increase the specificity above that of BI-RADS alone. As expected, when we combined BI-RADS with the set of Emax, Emean, SD and Eratio, the specificity and accuracy for differentiation of benign from malignant breast lesions improved significantly, without loss of
Conclusions
Serial interpretation of a set of SWE quantitative parameters (Emax, Emean, SD and Eratio) with ultrasound BI-RADS criteria, with a positive SWE (at least one abnormal parameter) and a high BI-RADS score being counted as “malignant,” seems to improve the accuracy of US in differentiation of benign from malignant breast lesions, without loss of sensitivity.
Acknowledgments
This research was supported by Special Funds of the National Natural Science Foundation of China (Grant 81241055).
References (22)
- et al.
Elastography: A quantitative method for imaging the elasticity of biological tissues
Ultrason Imaging
(1991) - et al.
Quantitative assessment of breast lesion viscoelasticity: Initial clinical results using supersonic shear imaging
Ultrasound Med Biol
(2008) Breast Imaging Reporting and Data System (BI-RADS)—Ultrasound
(2003)- et al.
Breast lesions: Quantitative elastography with supersonic shear imaging—Preliminary results
Radiology
(2010) - et al.
Evaluation of breast lesions using sonographic elasticity imaging: A multicenter trial
J Ultrasound Med
(2012) - et al.
BE1 Investigators. Shear-wave elastography improves the specificity of breast US: The BE1 multinational study of 939 masses
Radiology
(2012) - et al.
Use of shear wave elastography to differentiate benign and malignant breast lesions
Diagn Interv Radiol
(2014) - et al.
Clinical application of shear wave elastography (SWE) in the diagnosis of benign and malignant breast disease
Breast Cancer Res Treat
(2011) - et al.
BE1 Study Group. Shear wave elastography for breast masses is highly reproducible
Eur Radiol
(2012) - et al.
Solid breast mass characterisation: Use of the sonographic BI-RADS classification
Radiol Med
(2007)