A mammogram is an x-ray of the breast. A diagnostic mammogram is used to diagnose breast disease in women who have breast symptoms or an abnormal result on a screening mammogram. Screening mammograms are used to look for
breast disease in women who are asymptomatic; that is, those who appear to have no breast problems. Screening mammograms usually take 2 views (x-ray pictures taken from different angles) of each breast. Women who are breast-feeding can still get mammograms, although these are probably not quite as accurate because the breast tissue tends to be dense.
For some women, such as those with breast implants (for augmentation or as reconstruction after mastectomy), additional pictures may be needed to include as much breast tissue as possible. Breast implants make it harder to see breast tissue on standard mammograms, but additional x-ray pictures with implant displacement and compression views can be used to more completely examine the breast tissue. If you have implants, it is important that you have your mammograms done by someone skilled in the techniques used for women with implants.
Although breast x-rays have been performed for more than 70 years, modern mammography has only existed since 1969. That was the first year x-ray units dedicated to breast imaging were available. Modern mammogram equipment designed for breast x-rays uses very low levels of radiation, usually about a 0.1 to 0.2 rad dose per x-ray (a rad is a measure of radiation dose).
Strict guidelines ensure that mammogram equipment is safe and uses the lowest dose of radiation possible. Many people are concerned about the exposure to x-rays, but the level of radiation used in modern mammograms does not significantly increase the risk for breast cancer.
To put dose into perspective, a woman who receives radiation as a treatment for breast cancer will receive several thousand rads. If she had yearly mammograms beginning at age 40 and continuing until she was 90, she will have received 20 to 40 rads. As another example, flying from New York to California on a commercial jet exposes a woman to roughly the same amount of radiation as one mammogram.
For a mammogram, the breast is compressed between 2 plates to flatten and spread the tissue. Although this may be uncomfortable for a moment, it is necessary to produce a good, readable mammogram. The compression only lasts a few seconds. The entire procedure for a screening mammogram takes about 20 minutes.
The x-ray machine for mammography
The procedure produces a black and white image of the breast tissue either on a large sheet of film or as a digital computer image that is "read," or interpreted, by a radiologist (a doctor trained to interpret images from x-rays, ultrasound, magnetic resonance imaging, and related tests.)
What the doctor looks for on your mammogram
The doctor reading the films will look for several types of changes:
Calcifications are tiny mineral deposits within the breast tissue that appear as small white spots on the films. They may or may not be caused by cancer. Calcifications are divided into 2 types:
A mass, which may occur with or without calcifications, is another important change seen on mammograms. Masses can be many things, including cysts (non-cancerous, fluid-filled sacs) and non-cancerous solid tumors (such as fibroadenomas). Masses that are not cysts usually need to be biopsied.
Having your previous mammograms available for the radiologist is very important. They can be helpful to show that a mass or calcification has not changed for many years. This would mean that it is probably a benign condition and a biopsy is not needed.
Limitations of mammograms
A mammogram cannot prove that an abnormal area is cancer. To confirm whether cancer is present, a small amount of tissue must be removed and looked at under a microscope. This procedure is called a biopsy. For more information, see the separate American Cancer Society document, For Women Facing a Breast Biopsy.
You should also be aware that mammograms are done to find cancers that can't be felt.. If you have a breast lump, you should have it checked by your doctor, who may recommend a biopsy even if your mammogram result is normal.
For some women, such as those with breast implants, additional pictures may be needed. Breast implants make it harder to see breast tissue on standard mammograms, but additional x-ray pictures with implant displacement and compression views can be used to more completely examine the breast tissue.
Mammograms are not perfect at finding breast cancer. They do not work as well in younger women, usually because their breasts are dense and can hide a tumor. This may also be true for pregnant women and women who are breast-feeding. Since most breast cancers occur in older women, this is usually not a major concern.
However, this can be a problem for young women who are at high risk for breast cancer (due to gene mutations, a strong family history of breast cancer, or other factors) because they often develop breast cancer at a younger age. For this reason, the American Cancer Society now recommends MRI scans in addition to mammograms for screening in these women. (MRI scans are described below.) For more information, also see the separate American Cancer Society document, Mammograms and Other Breast Imaging Procedures.
Tips for having a mammogram
The following are useful suggestions for making sure that you receive a quality mammogram:
What to expect when you get a mammogram
If you are a woman and age 40 or over, you should get a mammogram every year. You can schedule the next one while you're there at the facility. Or, you can ask for a reminder to schedule it as the date gets closer.
For more information on mammograms and other imaging tests for early detection and diagnosis of breast diseases, refer to the American Cancer Society document, Mammograms and Other Breast Imaging Procedures.
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