Mammography is a specific type of imaging that uses a low dose x-ray system for examination of the breasts. Most medical experts agree that successful treatment of breast cancer is linked to early detection. Mammography plays a central role in the detection of breast cancer because it can show changes in the breast up to two years before a patient or physician can feel them. Current guidelines from the U.S. Department of Health and Human Services, the American Cancer Society, the American Medical Association, and the American College of Radiology recommend screening mammography every year for women, beginning at age 40.

Mammography is used to aid in the diagnosis of breast diseases in women. As with all x-ray examinations, mammograms provide valuable information about your health and play an important role in helping your doctor make an accurate diagnosis. Mammography can assist your physician in the detection of disease even if you have no complaints or symptoms. It can be used to evaluate a patient with abnormal physical exam findings, such as a breast lump, that has been found by a woman or her doctor.

X-rays are a form of radiant energy, like light or radio waves. Unlike light, x-rays can penetrate the body, which allows a radiologist to produce pictures of internal structures.

During mammography, the breast is exposed to a small dose of radiation to produce an image of internal breast tissue. The image of the breast is produced as a result of x-rays passing through the breast to expose either a film or digital image receptor. The radiologist can view these images on photographic film or on a computer. X-rays are produced only when a switch is momentarily turned on. As with visible light, no radiation remains after the switch is turned off.

The scientific unit of measurement for radiation dose, commonly referred to as effective dose, is the millisievert (mSv). The effective dose accounts for the relative sensitivity of the different tissues exposed. More importantly, it allows for quantification of risk and comparison to more familiar sources of exposure that range from natural background radiation to radiographic medical procedures.

We are exposed to radiation from natural sources all the time. The average person in the U.S. receives an effective dose of about 3 mSv per year from naturally occurring radioactive materials and cosmic radiation from outer space. These naturally occurring background radiation doses vary throughout the country and with elevation. For example, persons living in the plateaus of Colorado receive about 1.5 mSv more radiation per year (due to cosmic radiation) compared to persons living at sea level.

We can compare the radiation exposure from x-rays as equivalent to the amount of radiation exposure one experiences from our natural surroundings. The effective radiation dose from a mammogram is about 0.7 mSv (millisievert), which is about the same as the average person receives from naturally occurring background radiation in three months. In contrast, radiation therapy doses used in the treatment of cancer are usually several thousand times greater. The federal mammography guidelines require that a medical physicist evaluate mammography equipment each year to be sure that the unit operates correctly and that effective radiation doses are controlled.

As with other medical procedures, x-rays are safe when used with care. Radiologists and technologists have been trained to use the minimum amount of radiation necessary to obtain the needed results. The amount of radiation used in most examinations is very small and the benefit from having the exam greatly outweighs the risk of harm from the small radiation dose. Women having additional mammogram views, mammograms for wire localization, or images for stereotactic biopsy will receive a slightly higher radiation dose due to the increased number of images. Even so, the radiation dose received is still safe relative to the valuable information received from the images.

As with any aspect of medical care, knowing that a patient is or could be pregnant provides important information. Pregnancy, for example, might explain certain symptoms or medical findings. While the vast majority of medical x-rays do not pose a critical risk to the developing fetus, there may be a small likelihood of causing a serious illness or other complication. The actual risk depends on how far along the pregnancy is and on the type and amount of radiation. X-ray studies of the head, neck, arms, legs and chest do not usually expose the baby directly to radiation and typically the technologist who takes the x-rays will implement special precautions to ensure that the baby of a pregnant patient is not directly exposed.

If you have any additional questions, please do not hesitate to ask a technologist or radiologist. Information can also be found online at www.radiologyinfo.org.