In many countries routine mammography of older women is encouraged as a screening method to diagnose early breast cancer. The United States Preventive Services Task Force recommends screening mammography, with or without clinical breast examination, every 1-2 years for women aged 40 and older.

Like all x-rays, mammograms use doses of ionizing radiation to create images. Radiologists then analyze the image for any abnormal findings. It is normal to use longer wavelength X-rays (typically Mo-K) than those used for radiography of bones.

At this time, mammography along with physical breast examination is the modality of choice for screening for early breast cancer. Ultrasound, ductography, and magnetic resonance imaging are adjuncts to mammography. Ultrasound is typically used for further evaluation of masses found on mammography or palpable masses not seen on mammograms. Ductograms are still used in some institutions for evaluation of bloody nipple discharge when the mammogram is non-diagnostic. MRI can be useful for further evaluation of questionable findings as well as for screening pre-surgical evaluation in patients with known breast cancer to detect any additional lesions that might change the surgical approach, for instance from breast-conserving lumpectomy to mastectomy. New procedures, not yet approved for use in the general public, including breast tomosynthesis may offer benefits in years to come.

Mammography has a false-negative (missed cancer) rate of at least 10 percent. This is partly due to dense tissues obscuring the cancer and the fact that the appearance of cancer on mammograms has a large overlap with the appearance of normal tissues.

Procedure

During the procedure, the breast is compressed by a dedicated mammography machine to even out the tissue, to increase image quality, and to hold the breast still (preventing motion blur). Both front and side images of the breast are taken. Deodorant, talcum powder or lotion may show up on the X-ray as calcium spots, and women are discouraged from applying these on the day of their investigation.

Until some years ago, mammography was typically performed with screen-film cassettes. Now, mammography is undergoing transition to digital detectors, known as Full Field Digital Mammography (FFDM). This progress is some years later than in general radiology. This is due to several factors:

1. the higher resolution demands in mammography,
2. significantly increased expense of the equipment,
3. the fact that digital mammography has never been shown to be superior to film-screen mammography for the diagnosis of breast cancer.

Computed radiography (CR) may help speed the transition. CR allows facilities to continue to use their existing screen-film units but do the cassettes with an imaging plate that acts as a digital adapter.