Mammograms and Other Breast Imaging Tests

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Mammogram basics

What is a mammogram?

A mammogram is an x-ray of the breast.

Why do I need mammograms?

A mammogram can often find or detect breast cancer early, when it’s small and even before a lump can be felt. This is when it’s easiest to treat.

What are the types of mammograms?

Screening Mammograms

A screening mammogram is used to look for signs of breast cancer in women who don’t have any breast symptoms or problems. X-ray pictures of each breast are taken from 2 different angles.

Diagnostic Mammograms

Mammograms can also be used to look at a woman’s breast if she has a breast problem or a change is seen on a screening mammogram. When used in this way, they are called diagnostic mammograms. They may include extra views (images) of the breast that aren’t part of screening mammograms. Sometimes diagnostic mammograms are used to screen women who were treated for breast cancer in the past.

What do mammograms show?

Mammograms can’t prove that an abnormal area is cancer, but they can help health care providers decide whether more testing is needed. The 2 main types of breast changes found with a mammogram are calcifications and masses.

Calcifications are tiny mineral deposits within the breast tissue. They look like small white spots on the pictures. They may or may not be caused by cancer.

A mass, or tumor, may or may not have calcifications, and is another important change seen on mammograms. Masses can be many things, including cysts (fluid-filled sacs) and non-cancerous solid tumors, but they could also be cancer. Any mass that’s not clearly a simple fluid-filled cyst usually needs to be biopsied. (A biopsy is taking out a small piece of tissue to see if cancer cells are in it.)

Having your prior mammograms available for the radiologist is very important. They can help to show if a mass or calcification has changed over time, which could affect whether a biopsy is needed.

How do mammograms work?

A mammogram uses a machine designed to look only at breast tissue. The machine takes x-rays at lower doses than usual x-rays. Because these x-rays don’t go through tissue easily, the machine has 2 plates that compress or flatten the breast to spread the tissue apart. This gives a better picture and allows less radiation to be used.

A digital mammogram (also known as full-field digital mammography or FFDM) is like a standard mammogram in that x-rays are used to make pictures of the breast. The differences are in the way the picture is made, looked at, and stored. Standard mammograms are printed on large sheets of film. Digital images are recorded and saved as files in a computer. Digital mammograms are becoming more widely available. They may be better than standard film mammograms for some women, but they’re not clearly better for everyone. Women should not skip their regular mammogram because a digital one isn’t available.

A newer type of mammogram is known as breast tomosynthesis or 3D mammography. For this, the breast is compressed once and a machine takes many low-dose x-rays as it moves over the breast. A computer then puts the images together into a 3-dimensional picture. This uses more radiation than most standard 2-view mammograms, but it may allow doctors to see the breast tissues more clearly. Some studies have suggested it might lower the chance of being called back for follow-up testing. It may also be able to find more cancers. But not all health insurances cover tomosynthesis.

Are mammograms safe?

The benefits of mammography outweigh any possible harm from the radiation exposure. Modern machines use low radiation doses to get breast x-rays that are high in image quality. On average the total dose for a typical mammogram with 2 views of each breast is about 0.4 mSv. (A mSv is a measure of radiation dose.)

To put dose into perspective, people in the US are normally exposed to an average of about 3 mSv of radiation each year just from their natural surroundings. (This is called background radiation.) The dose of radiation used for a screening mammogram of both breasts is about the same amount of radiation a woman would get from her natural surroundings over about 7 weeks.

If there’s any chance you might be pregnant, let your health care provider and x-ray technologist know. Although the risk to the fetus is likely very small, screening mammograms aren’t routinely done in pregnant women.

Last Medical Review: 12/08/2014
Last Revised: 04/25/2016