Combined Elastography and Color Doppler Ultrasonography for Breast Screening With Ultrasound

* Asymptomatic women who undergo breast screening with ultrasound and has breast masses of Breast Imaging Reporting and Data System (BI-RADS) category 3 or higher will be examined with conventional B-mode US as well as combined elasto-doppler US by breast radiologists. * The likelihood of malignancy and BI-RADS category of the breast masses are assessed for each dataset of B-mode US alone and B-mode US with elasto-doppler US, respectively. * Reference standard: Biopsy or 1 year of follow-up examination. * The positive-predictive value, sensitivity, specificity, and diagnostic accuracy (assessed by the area under the receiver operating characteristic curve) are evaluated and compared between B-mode US alone and B-mode US with elasto-doppler US.