Traditional mammography uses low-dose X-rays that pass through breast tissue onto photographic film. Digital mammography also uses low-dose X-rays with the output read digitally on a computer. Digital mammography's advantages include images that can be more easily adjusted to improve the contrast of normal and abnormal breast tissue, magnified for closer inspection, and more conveniently stored facilitating comparisons over time. Digital mammography also provides more accurate results on younger women and women with denser breast tissue. Disadvantages include price, limited availability and insurance coverage.
Background
Digital mammography is one of several newer breast-imaging technologies developed to improve the detection of breast cancer in its earliest stages. Approved by the Food and Drug Administration in 2000, digital mammography is done the same way traditional mammography is done but, instead of the X-rays being detected on a photographic film, the X-rays are converted to digital images read by a computer.
Digitalized Images
Digitalizing the breast images has several advantages. Breast images are more easily reviewed by varying the tissue contrast levels and magnifying specific areas. In addition, the images can also be stored and compared to earlier images made of the same patient. Also, the computer can double check the radiologist's conclusions and generate a "second" opinion of the radiologist's reading.
Storage of the images and inclusion in digital patient records is also improved. Digital mammography also facilitates the transfer of a woman's mammogram records to other health care providers.
Accuracy of Diagnosis
In 2001, the National Cancer Institute, or NCI, part of the National Institutes of Health, sponsored a study comparing traditional film-based mammography to digital mammography to determine whether diagnosis of breast cancers was improved with digital mammography. The Digital Mammography Imaging Screening Trial, or DMIST, enrolled 49,528 women across the U.S. and Canada, giving women both digital and traditional film mammograms.
Results across the entire study population showed the two methods of mammography had similar accuracy in diagnosing breast cancers. DMIST did, however, show digital mammography was significantly better than film mammography in screening women who were under age 50, or women of any age who had very dense breasts.
DMIST did not find that digital mammography generated fewer false positives than traditional film mammography.
Disadvantages
Because advantages of digital mammography have not been significant for most women, not all insurers will cover digital mammograms. This reluctance is likely related to its higher cost.
In addition, digital mammography is still not widespread. Most U.S. facilities still use film-screen mammography.
American College of Radiology
Because the proven diagnostic advantages of digital mammography have been limited, the American College of Radiology's position issued in 2009 is that "for tens of millions of women, screen-film mammography is equally effective as digital. Women should continue to receive annual mammograms even if, at present, the new digital technology is not available in their communities."
References
- NIH: National Cancer Institute: Digital Mammograhphic Screening Trial.
- "Radiology": American College of Radiology Imaging Network Digital Mammographic Imaging Screening Trial: Objectives and Methodology: Etta D. Pisano et al.: 2005.
- American College of Radiology: ACR Statement Regarding the Digital Mammographic Imaging Screening Trial (DMIST) Results: 2009.
