Human soft tissue such as breast tissue has viscoelasticity property. However, most ultrasound has only been measured for elasticity and viscosity has been neglected. Shear wave elastography (SWE) is a ultrasound technique that quantifies tissue elasticity. Shear wave dispersion (SWD) imaging is a newly developed ultrasound technique that evaluates the dispersion slope of shear waves, which is related to the viscosity of biological tissues. The goal of this retrospective study was to compare diagnostic performance between SWE and SWD to distinguish benign from malignant breast masses and to investigate additional role of SWD. Using histological diagnosis of breast lesions as a standard reference, quantitative indices of SWE and SWD were evaluated to diagnose breast cancer, and the diagnostic performance of SWE and SWD was compared.

This retrospective study was approved by our institutional review board, which waved the requrement for informed consent. The investigators obtained quantitative parameters of SWE and SWD of solid breast lesions before biopsy. The investigators measured average tumor elasticity and tumor-to-fat elasticity ratio on SWE and average tumor dispersion and tumor-to-fat ratio and on SWD from each breast lesion. Diagnostic performance of SWE and SWD was compared using the area under the curve (AUC), sensitivity, specificity, and accuracy.

Inclusion Criteria:

• patients with histological results

Exclusion Criteria:

• patients without histological results

The study population should fulfill the following criteria as follows:(a) histologically confirmed breast lesions and (b) shear wave elastography and dispersion ultrasound performed before biopsy