Mammography is a specific type of imaging that uses a low-dose x-ray system for the examination of breasts. A mammography exam, called a mammogram, is used as a screening tool to detect early breast cancer in women experiencing no symptoms and to detect and diagnose breast disease in women experiencing symptoms such as a lump, pain or nipple discharge.
Mammography plays a central part in early detection of breast cancers 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 (HHS), the American Cancer Society (ACS), the American Medical Association (AMA) and the American College of Radiology (ACR) recommend screening mammography every year for women, beginning at age 40. Research has shown that annual mammograms lead to early detection of breast cancers, when they are most curable and breast-conservation therapies are available.
The National Cancer Institute (NCI) adds that women who have had breast cancer and those who are at increased risk due to a genetic history of breast cancer should seek expert medical advice about whether they should begin screening before age 40 and about the frequency of screening.
See the Breast Cancer page for information about breast cancer therapy.
While mammography is the best screening tool for breast cancer available today, mammograms do not detect all breast cancers. Also, a small portion of mammograms indicate cancer is present when it is not (called a false-positive result).
Research is being done on a variety of breast imaging techniques that can contribute to the early detection of breast cancer and improve the accuracy in distinguishing non-cancerous breast conditions from breast cancers.
Computer-aided detection (CAD) systems and digital mammography are some of the new technologies under study.
Digital mammography, also called full-field digital mammography (FFDM), is a mammography system in which the x-ray film is replaced by solid-state detectors that convert x-rays into electrical signals. These detectors are similar to those found in digital cameras. The electrical signals are used to produce images of the breast that can be seen on a computer screen or printed on special film similar to conventional mammograms. From the patient's point of view, digital mammography is essentially the same as the screen-film system.
See "Full-Field Digital Mammography: A Potential Alternative to the Traditional Film-Screen Technique?" under the News heading for more information on how FFDM works and its potential advantages.
Computer-aided detection (CAD) systems use a digitized mammographic image that can be obtained from either a conventional film mammogram or a digitally acquired mammogram. The computer software then searches for abnormal areas of density, mass, or calcification that may indicate the presence of cancer. The CAD system highlights these areas on the images, alerting the radiologist to the need for further analysis.
Mammography is used to aid in the diagnosis of breast diseases in women.
Screening mammography can assist your physician in the detection of disease even if you have no complaints or symptoms.
Initial mammographic images themselves are not always enough to determine the existence of a benign or malignant disease with certainty. If a finding or spot seems suspicious, your radiologist may recommend further diagnostic studies.
Diagnostic mammography is used to evaluate a patient with abnormal clinical findings—such as a breast lump or lumps—that have been found by the woman or her doctor. Diagnostic mammography may also be done after an abnormal screening mammography in order to determine the cause of the area of concern on the screening exam.
Before scheduling a mammogram, the American Cancer Society (ACS) and other specialty organizations recommend that you discuss any new findings or problems in your breasts with your doctor. In addition, inform your doctor of any prior surgeries, hormone use, and family or personal history of breast cancer.
Do not schedule your mammogram for the week before your period if your breasts are usually tender during this time. The best time for a mammogram is one week following your period. Always inform your doctor or x-ray technologist if there is any possibility that you are pregnant.
The ACS also recommends you:
Do not wear deodorant, talcum powder or lotion under your arms or on your breasts on the day of the exam. These can appear on the mammogram as calcium spots.
Describe any breast symptoms or problems to the technologist performing the exam.
If possible, obtain prior mammograms and make them available to the radiologist at the time of the current exam.
Ask when your results will be available; do not assume the results are normal if you do not hear from your doctor or the mammography facility.
In addition, before the examination you will be asked to remove all jewelry and clothing above the waist and you will be given a gown or loose-fitting material that opens in the front.
A mammography unit is a rectangular box that houses the tube in which x-rays are produced. The unit is used exclusively for x-ray exams of the breast, with special accessories that allow only the breast to be exposed to the x-rays. Attached to the unit is a device that holds and compresses the breast and positions it so images can be obtained at different angles.
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 some of the x-rays being absorbed, while others pass through the breast to expose either a film (conventional mammography) or digital image receptor (digital mammography). The exposed film is placed in a developing machine, producing images much like the negatives from a camera; digital images are stored on a computer.
During mammography, a specially qualified radiologic technologist will position your breast in the mammography unit. Your breast will be placed on a special platform and compressed with a paddle (often made of clear Plexiglas or other plastic).
Breast compression is necessary in order to:
Even out the breast thickness so that all of the tissue can be visualized.
Spread out the tissue so that small abnormalities won't be obscured by overlying breast tissue.
Allow the use of a lower x-ray dose since a thinner amount of breast tissue is being imaged.
Hold the breast still in order to eliminate blurring of the image caused by motion.
Reduce x-ray scatter to increase sharpness of picture.
The technologist will stand behind a glass shield during the x-ray exposure. You will be asked to change positions slightly between images. The routine views are a top-to-bottom view and an oblique side view. The process will be repeated for the other breast.
The examination process should take about half an hour. When the mammography is completed you will be asked to wait until the technologist examines the images to determine if more are needed.
You will feel pressure on the breast as it is squeezed by the compressor. Some women with sensitive breasts may experience discomfort. If this is the case, schedule the procedure when your breasts are least tender. The technologist will gradually compress your breast. Be sure to inform the technologist if pain occurs as compression is increased. If discomfort is significant, less compression will be used.
A radiologist, who is a physician experienced in mammography and other x-ray examinations, will analyze the images, describe any abnormalities, and suggest a likely diagnosis. The report will be dictated by the radiologist and then sent to your referring physician. You will also be notified of the results by the mammography facility.
Imaging of the breast improves a physician's ability to detect small tumors. When cancers are small, the woman has more treatment options and a cure is more likely.
The use of screening mammography increases the detection of small abnormal tissue growths confined to the milk ducts in the breast, called ductal carcinoma in situ (DCIS). These early tumors cannot harm patients if they are removed at this stage and mammography is the only proven method to reliably detect these tumors.
The effective radiation dose from a mammogram is about 0.7 mSv, which is about the same as the average person receives from background radiation in three months. Federal mammography guidelines require that each unit be checked by a medical physicist every year to ensure that the unit operates correctly. See the Safety page for more information about radiation dose.
Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant. See the Safety page for more information about pregnancy and x-rays.
False Positive Mammograms. Five percent to 15 percent of screening mammograms require more testing such as additional mammograms or ultrasound. Most of these tests turn out to be normal. If there is an abnormal finding a follow-up or biopsy may have to be performed. Most of the biopsies confirm that no cancer was present. It is estimated that a woman who has yearly mammograms between ages 40 and 49 has about a 30 percent chance of having a false-positive mammogram at some point in that decade and about a 7 percent to 8 percent chance of having a breast biopsy within the 10-year period.
The estimate for false-positive mammograms is about 25 percent for women ages 50 or older.