How is a mammogram done?

When you have a mammogram, your breast is briefly compressed or squeezed between 2 plates attached to the mammogram machine—an adjustable plastic plate (on top) and a fixed x-ray plate (on the bottom). The bottom plate holds the x-ray film, or the digital detector that makes the image. The technologist compresses your breast to keep it from moving, and to make the layer of breast tissue thinner. These steps reduce the x-ray exposure and make the picture sharper. Although the compression can feel uncomfortable and even painful for some women, it only lasts a few seconds and is needed to get a good picture. Talk to the technologist if you have pain. She can reposition you to make the pressure as comfortable as possible. The entire procedure for a mammogram takes about 20 minutes.

The x-ray device and compression plates used for mammograms

Mammograms produce a black and white x-ray picture of the breast tissue. Depending on the type of machine, the picture is either on a large sheet of film or is an electronic image that can be seen on a computer screen. These two ways of doing a mammogram are much the same. The differences are in the way the picture is recorded, looked at by the doctor, and stored.

Screen-film units are the machines that produce the mammogram picture on x-ray film. Full-field digital mammography units capture the picture in a digital format that can be looked at on a computer screen. Most mammogram machines in use today are full-field digital units.

For the most part, regular screen-film mammograms are as accurate as digital mammograms. But digital mammograms have been shown to have some unique advantages. Some studies have found that women who have questionable areas on their mammogram have to return less often for extra imaging tests because with digital mammograms, the original pictures can be magnified and looked at in many different ways on the computer screen. Several studies have also found that digital mammograms were more accurate in finding cancers in women younger than 50 and in women with dense breast tissue.

It’s important to remember that standard film mammograms also work well for these groups of women, and that women should still get their regular mammograms, even if digital mammography is not available.

No matter what kind of x-ray image is taken – film or electronic – it’s interpreted (or “read”) by a doctor, most often a radiologist. Radiologists are doctors who have special training in diagnosing diseases by looking at pictures of the inside of the body produced by x-rays, sound waves, magnetic fields, or other methods. Other doctors who treat breast diseases may look at the mammogram, too.

Reading mammograms is challenging. The way the breast looks on a mammogram varies a great deal from woman to woman. And some breast cancers may cause changes in the mammogram that are hard to notice.

If you have had mammograms in the past, it’s very important that the radiologist has your most recent x-ray films or digital pictures so they can be compared with the new ones. (The actual pictures are needed, not just the report.) Comparing the pictures helps the doctor find small changes and detect cancer as early as possible. Because it can be hard to get your older pictures, it’s best to find a facility that you are comfortable with and plan to get your regular mammograms there each year. That way, your mammogram pictures are all in one place.

Tips for having a mammogram

These tips can help you have a good quality mammogram:

• If it’s not posted in a place you can see it near the receptionist’s desk, ask to see the FDA certificate that’s issued to all facilities that offer mammograms. The FDA requires all facilities to meet high professional standards of safety and quality in order to provide mammogram services. Facilities that are not certified may not provide mammogram services.
• Use a facility that specializes in mammograms and does many mammograms a day.
• If you are satisfied that the facility is of high quality, continue to go there on a regular basis so that your mammograms can easily be compared from year to year.
• If you’re going to a facility for the first time, bring a list of the places, and dates of mammograms, biopsies, or other breast treatments you have had before.
• If you have had mammograms at another facility, you should try to get those mammograms to bring with you to the new facility (or have them sent there) so that they can be compared to the new ones.
• On the day of the exam, don’t wear deodorant or antiperspirant. Some of these contain substances that can show up on the x-ray as white spots. If you’re not returning home, you may want to take your deodorant with you to put on after your exam.
• You may find it easier to wear a skirt or pants, so that you’ll only need to remove your top and bra for the mammogram.
• Schedule your mammogram when your breasts are not tender or swollen to help reduce discomfort and get a good picture. If you are still menstruating, try to avoid the week just before your period.
• Always describe any breast changes or problems you are having to the technologist doing the mammogram. Also describe any medical history that could affect your breast cancer risk—such as surgery, hormone use, or breast cancer in your family (or if you’ve had breast cancer before). Discuss any new findings or problems in your breasts with your doctor or nurse before having the mammogram.
• Before having any type of imaging test, tell the radiologic technologist if you are breast-feeding or if you think you might be pregnant.
• If you do not hear from your doctor within 10 days, do not assume that your mammogram was normal; call your doctor or the facility.

What to expect when you have a mammogram

• You will have to undress above the waist to have a mammogram. The facility will give you a wrap to wear.
• A technologist will position your breasts for the mammogram. You and the technologist are the only ones in the room during the mammogram.
• To get a high-quality picture, the breast must be flattened. The technologist places the breast on the machine’s metal plate. The plastic upper plate is lowered to compress the breast for a few seconds while the technologist takes a picture.
• The whole procedure takes about 20 minutes. The actual breast compression only lasts a few seconds.
• You may feel some discomfort or even pain when your breasts are compressed, and for some women it can be painful.
• All mammogram facilities are now required to send your results to you within 30 days. In most cases, you will be contacted within 5 working days if there’s a problem with the mammogram.
• Being called back for more testing does not mean that you have cancer. In fact, less than 10% of women called back for more tests are found to have breast cancer. Being called back occurs fairly often. It usually just means more pictures or an ultrasound needs to be done to look at a suspicious area more carefully.
• Only 2 to 4 screening mammograms of every 1,000 lead to a diagnosis of breast cancer.

If you are a woman age 40 or over, you should get a mammogram every year. (See our document called Breast Cancer: Early Detection for the American Cancer Society breast cancer screening recommendations.) 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. Some women schedule the next year’s mammogram and ask to be reminded of the appointment a few weeks ahead of time.