Diagnostic performance of digital breast tomosynthesis (DBT) would be not inferior to the that of breast ultrasound in women with dense breast.

1. Patients with dense breast will be examined for the detection of breast cancer by imaging studies.
2. The imaging including digital breast tomosynthesis (DBT), physician-performed bilateral whole breast ultrasonography will be performed according to a standard protocol.Interpretation will be conducted independently and classified according to the Breast Imaging Reporting and Data System (BI-RADS) by experienced radiologists.
3. Definitive information about the presence of malignancy will be obtained by biopsy directed by the imaging method best depicting the lesion with 14-g or 11-g needle devices or needle localized excision. The absence of breast cancer was determined by means of biopsy, the absence of positive findings on repeat imaging and clinical examination, or both at follow-up.
4. The diagnostic yield of digital breast tomosynthesis (DBT) compared to ultrasonography will be assessed.

Inclusion Criteria:

• Women aged at 20 years
• Women who had heterogeneously dense or extremely dense parenchyma, either by prior mammography report or by review of prior mammograms
• Signed study-specific informed consent prior to registration

Exclusion Criteria:

• Had breast surgery
• Had breast core biopsy performed within the prior 6 months on the study

Women undergoing mammography and breast US for screening or diagnostic purpose