Ultrasound, also called sonography, is an imaging technique in which high-frequency sound waves that cannot be heard by humans are bounced off tissues and internal organs. Their echoes produce a picture called a sonogram. Ultrasounds imaging of the breast is used to distinguish between solid tumors and fluid-filled cysts. Ultrasound can also be used to evaluate lumps that are hard to see on a mammogram. Sometimes, ultrasound is used as part of other diagnostic procedures, such as cyst aspiration or breast biopsy. Breast biopsy is the removal of tissue with a needle for examination under a microscope to check for signs of cancer.

During an ultrasound examination, the clinician spreads a thin coat of lubricating jelly over the area of the breast to be imaged to improve the conduction of the sound waves. A hand-held device called a transducer directs sound waves through the skin toward specific tissues. As the sound waves are reflected back from the tissues within the breast, the patterns formed by the waves create a two-dimensional image of the breast on a computer, which can provide an image of a mass within the breast.

Ultrasound is not used for routine breast cancer screening because it does not consistently detect certain early signs of cancer such as microcalcifications (tiny deposits of calcium in the breast that cannot be felt but can be seen on a conventional mammogram). A cluster of microcalcifications may indicate that cancer is present. Abnormalities found on ultrasound may be biopsied using ultrasound guidance, at the time of your appointment. The needle used for the biopsy can be seen in "real time" or "live" by the radiologist as the tissue is biopsied with ultrasound guidance.

- National Cancer Institute

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