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Digital Mammography Compares Well With Film Mammography

New and Old Machines Equally Accurate - Younger Women Benefit Most

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Updated June 15, 2010

Stereo Digital Mammography

Stereo Digital Mammography

Photo © Dr. David Getty
A digital mammogram machine uses compression and x-rays to image your breast, but instead of capturing the image on film as with traditional mammography, the image is captured to a computer as a digital image file. Also called a full-field digital mammogram (FFDM), this technology compares well with film mammography and will benefit younger women the most.

Advantages of Digital Mammography
Digital mammograms are faster than film mammograms, because there is no film to develop. The image can be sent immediately to the radiologist for viewing. If the image is unclear, you will be told about it right away, and the image can be retaken. This may help reduce mammogram callbacks, and stress on patients. The National Cancer Institute did a study comparing film and digital mammography, and concluded that digital mammography is more accurate than film at finding cancer in women less than 50 years old, and women who have dense (not fatty) breast tissue. Digital mammography uses less radiation than traditional film mammography, reducing your lifetime exposure to x-rays.

Doing More with Digital Mammogram Images
Once your mammogram images are in the computer, your radiologist can view them on a monitor, much as you would look at digital photos. On the computer, your radiologist can closely examine the images by zooming in, adjusting the image brightness, or changing the contrast, making all areas of the breast easier to see. If your doctor wants to consult a breast specialist about your mammograms, the digital image files can be electronically sent to other sites for examination (telemammography). Computer-aided detection and diagnosis (CAD) can be used on the digital images to help your doctor analyze the overall images, and flag areas that need closer study. CAD can find tumors that a radiologist might not spot. Once a CAD analysis has been done, a radiologist will do a visual check of those areas, and based on training and experience, decide how serious the mass may actually be.

Stereo Digital Mammography Makes Three-Dimensional Images
On the research horizon, stereo digital mammograms are being done in clinical trials for women who were called back after an abnormal routine mammogram. A stereo digital mammogram combines two digital breast x-rays taken from different angles, and produces a detailed three-dimensional image of your breast's internal structure. Such stereo images must be viewed on a special workstation by a specially trained radiologist. The study was led by Dr. David J. Getty of BBN Technologies of Cambridge, Mass, and presented at Radiological Society of North America in November 2007. "In our study, stereo digital mammography reduced false positives by 49 percent," said Dr. Getty. "This could have a significant impact by cutting in half the number of women who are needlessly recalled for additional diagnostic work-ups, resulting in a large savings in cost and patient anxiety."

The Digital Mammographic Imaging Screening Trial
The American College of Radiology Imaging Network (ACRIN) teamed up with the National Cancer Institute in 2001 to conduct a study that compared film and digital mammography. The study was called the Digital Mammographic Imaging Screening Trial (DMIST). This study recruited 49,500 participants, all of whom received film and digital mammograms and follow-up studies. So how do these technologies compare?

  • Film and digital mammograms have similar screening accuracy for the general population
  • Rates of false positives (incorrect diagnosis of cancer) were the same for both methods
  • Both technologies are 92% accurate at ruling out breast cancer
Some women do benefit more than others, and they meet these at least one of these qualifications:
  • Younger than 50 years old, regardless of breast density
  • Any age, with very dense, or extremely dense breast tissue (very little fatty tissue)
  • Pre- or perimenopausal women, regardless of age
Comparing Cost and Availability
Film mammography is widely available, and is covered by most health insurance providers. Digital mammography is already available in many major cities and nearby locations, but may not be found everywhere just yet. Digital mammography systems cost about 1.5 to 4 times more than film systems. Several different companies make digital mammography systems that have been given FDA approval.

Take-home Message About Digital Mammograms
Traditional film mammography has been done for 35 years, with a high degree of success. You should have your annual mammogram on schedule, whether or not you have access to the digital technology. Skipping a mammogram throws off the yearly comparison with your previous results. If you've had your regular mammogram on film, you don't need to get a digital image done as well –- if digital mammography is available to you in the following year, it will be compared with your film study. If you are under 50 years old, premenopausal, or have dense breast tissue, you will benefit from digital mammography, and should take advantage of it, if it's available to you.

Sources:
American Cancer Society. Breast Cancer: Early Detection - Importance of Finding Breast Cancer Early. Full-field Digital Mammograms (FFDM). Revised: 09/17/2007.

National Cancer Institute. Digital vs. Film Mammography in the Digital Mammographic Imaging Screening Trial (DMIST): Questions and Answers. Posted: 09/16/2005.

RSNA 2007. Improved Accuracy of Lesion Detection in Breast Cancer Screening with Stereoscopic Digital Mammography. Presented by David Getty, Ph.D.

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