Breast ultrasound refers to the process of using medical ultrasonography

Medical ultrasonography

Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...

 to perform imaging of the breast.

It can be considered either a diagnostic or a screening procedure.

It may be used either with or without a mammogram.

It may be useful in younger women, where the denser fibrous tissue of the breast may make mammograms more difficult to interpret.