Ultrasound of the breast is the most common imaging test that is used to complement mammography. Because ultrasound (sonogram) does not show some signs of breast cancer as well as mammography, such as calcifications and architectural distortion, it does not replace mammography for breast cancer screening, but adds to the proven benefits of mammography. It employs no ionizing radiation, does not require intravenous contrast material, is well-tolerated, and is widely available. Optimal results depend on having high-resolution ultrasound equipment and skilled technologists/ radiologists.
The most common indications for breast ultrasound include:
(1) evaluation of palpable lumps and other breast symptoms;
(2) evaluation of abnormal findings on mammography, MRI, or molecular breast imaging;
(3) screening for cancer in women with dense breasts;
(4) evaluation of breast implants for leaks, especially silicone.
Various studies have shown that the addition of ultrasound to mammography in high-risk women with dense breast tissue increases detection of breast cancer. The ACRIN 6666 multi-center study found that in this group of women, the addition of ultrasound to mammography detected an additional 7.2 cancers per 1,000 women. The sensitivity of combined mammography and ultrasound was 77.5%, compared to 49% with mammography alone. Additionally, 29% of the cancers were visualized only by ultrasound. The main drawback of screening with ultrasound was its relatively high false-positive rate, which resulted in additional biopsies and cost.
Breast elastography was developed to increase the accuracy of breast ultrasound by eliminating many of its false-positives (false alarms). Elastography uses ultrasound waves to determine how stiff or hard masses seen on ultrasound are. Soft masses are very likely to be benign and therefore can be followed closely, instead of being biopsied. Hard masses have a higher chance of being cancerous and therefore require a biopsy. Elastography requires special ultrasound units with elastography capability, which are available at Weinstein Imaging Associates.
