Mammograms and Other Breast Imaging Tests

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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. A thinner layer of breast tissue allows the x-ray exposure to be reduced and makes 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. Although the time you are exposed to x-rays is just seconds, the entire procedure for a mammogram takes about 20 minutes.

    The x-ray device and compression plates used for mammograms

Types of mammogram machines

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.

Digital mammograms may be better than film mammograms at finding cancers in women younger than 50 and in women with dense breast tissue. In the United States, most mammograms are digital.

It’s important to remember that standard film mammograms still work well. Nobody should miss having a regular mammogram because a digital mammogram is not available.

How mammograms are read

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. Some breast cancers may cause changes in the mammogram that are hard to notice.

If you’ve 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 doctor will want to look at the actual pictures, not just the reports. Comparing the pictures helps the doctor find small changes and detect cancer as early as possible. It can be hard to get your older pictures, so 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. If you do have to change facilities, call ahead to find out what you will need to do in order to get your old pictures to be taken or sent to the new place.

Last Medical Review: 12/10/2013
Last Revised: 11/05/2014