What is the role of mammography in breast cancer screening?

Updated: Oct 17, 2016
  • Author: Nagwa Dongola, MD, FRCR; Chief Editor: Peter Eby, MD  more...
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Answer

Mammography is a special type of x-ray imaging used to create detailed images of the breast. It is estimated that 48 million mammograms are performed each year in the US. Mammography uses low dose x-rays, achieved by using targets made of low atomic weight alloys (eg, molybdenum and rhodium). Filters made of aluminum, molybdenum, beryllium, rhodium, or palladium are used to eliminate photons that do not contribute to the image, thereby minimizing the radiation dose to the patient.

Breast compression is necessary to flatten the breast so that the maximum amount of tissue can be imaged and examined. It also allows for a lower x-ray dose and immobilization of the breast to reduce motion blur. Compression also reduces x-ray scatter, which may degrade the image. Breast compression may cause some discomfort, but it should not cause any significant pain.

Randomized controlled trials in the 1970s and 80s used high-contrast, high-resolution (with single-sided emulsion) film to demonstrate findings smaller than 100 µm, such as microcalcifications. Nearly all film-based units in the United States have since been replaced with digital mammography systems.

In 2005, the American College of Radiology Imaging Network (ACRIN) published results of a multicenter trial comparing the diagnostic performance of film-screen to digital mammography. [5] The results indicated equivalent overall performance for the 2 modalities. However, in subgroup analysis, digital mammography performed better for women with dense breasts, premenopausal women, and women younger than 50 years. Since then, there has been a gradual national and international shift away from film-screen to digital mammography.

Mammography plays a major role in the early detection of breast cancers, detecting about 75% of cancers at least a year before they can be felt. Mammography uses low-dose ionizing radiation. Patients receive less radiation from a mammogram than from background environmental sources each year. The significant reduction in breast cancer mortality far outweighs the risks and inconvenience of the test.


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