Breast ultrasonography is an imaging technique used to assess abnormalities of the breast tissue. This technology uses sound waves to evaluate underlying structures, and is helpful because it is simple to do and does not expose women to radiation. The use of this imaging study has limitations, however, because it has a relatively poor ability to pick up on minor details — a property known as resolution — as compared to mammography. Applications of breast ultrasonography include the evaluation of masses detected on manual examination and the localization of breast masses during biopsies.
The technology of breast ultrasonography uses ultrasound waves, which are high-frequency sound waves inaudible to the human ear. A transducer is used to emit these sound waves, and the time it takes for the emitted wave to be returned to the transducer is recorded. From this information, the ultrasound machine is able to reconstruct a two-dimensional image of the underlying structures.
Using breast ultrasonography has a number of different benefits. Unlike radiographic techniques such as computed tomography (CT) scans, this imaging modality does not use dangerous ionizing radiation that could damage the underlying tissue with repeated exposure. Breast ultrasonography is also simple to do, does not typically cause the patient any pain or discomfort, and is fairly low cost.
Unfortunately, there are also some downsides to using breast ultrasonography. Often, the images obtained from the procedure are only as good as the technologist who did the study. The results of the procedure can also be distorted by excess levels of subcutaneous fat. Ultrasound can identify large masses, but typically doesn’t have enough resolution to detect masses that are less than 0.5 inch (1.27 cm) in diameter.
The most common use of breast ultrasonography is to evaluate masses found in the breast tissue. It is excellent for differentiating solid masses, which might be suggestive of a tumor, from cystic masses that are fluid-filled and often benign. Often ultrasounds are used to assist a doctor in performing a biopsy of a breast mass, as the doctor is able to guide the needle in real-time based on its approach to the mass. Breast ultrasound is also helpful in identifying the lymph nodes surrounding the breast, which are important because malignant tumors often spread to these lymph nodes, causing them to enlarge.
Routine breast ultrasonography is not typically used as a method to screen for breast cancer, as mammography has a more sophisticated ability to detect small masses. It does, however, play a role in evaluating masses detected on manual breast examination, especially in women under the age of 40. In a younger population, mammography has a decreased resolution because the breast tissue of these women is too dense. As a result, ultrasonography often provides more information in these younger patients.