In film mammograms, the images of your breasts are recorded on large sheets of black and white film. In digital mammograms, the images are recorded into a computer. Digital mammograms are thought to offer two advantages over film mammograms:
- less radiation exposure per breast image
- a better breast image, especially in younger women with dense breasts (breast that have a lower-than-average amount of fat tissue)
Usually two images are taken of each breast (four total images) in both digital and film screening mammograms. Sometimes more images are needed to provide a good reading.
In a large study, researchers analyzed how much radiation 5,102 women were exposed to during screening mammograms. The women were participating in a much larger digital mammography study called Digital Mammographic Imaging Screening Trials (DMIST). Nearly 50,000 women were part of DMIST from October 2001 through October 2003.
The researchers found that 21% of women who had digital mammograms needed more than four images taken while only 12% of women who had film mammograms needed more than four images. Among women who needed only the usual four breast images, women who had digital mammograms were exposed to an average 22% less radiation than women who had film mammography. But when the researchers evaluated the average radiation exposure of all of the women, including those who needed extra images, the average radiation exposure with digital mammography was only 17% lower than with film mammography.
There were large differences in the level of radiation exposure needed to produce a good breast image, depending on the manufacturer of the mammogram equipment.
Also, the average amount of pressure applied to the breast to produce a good image was less with digital mammograms.
The researchers also noted that advances have been made in digital mammogram technology, so the results of this study (from 2001 to 2003) may be different today. Still, these results may be important for researchers comparing the overall risks and benefits of different breast cancer screening approaches.
When developing your breast cancer screening plan, you and your doctor will likely discuss the availability of digital mammography in your area and whether it offers advantages for you. Here are some questions you may want to ask your doctor:
- If you're younger than 50 and premenopausal, ask your doctor about your breast density. If your breasts are dense, ask if digital mammograms are a better choice for you.
- If you're older than 65, postmenopausal, and have breasts that aren't dense, ask your doctor if film mammograms are a better choice for you.
Together you and your doctor can decide on the best screening approach for you based on your unique situation. To learn more about mammography techniques, visit the Breastcancer.org pages on Mammograms.
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