Mammography by the numbers
October 29, 1999
Web posted at: 12:02 PM EDT (1602 GMT)
By Lisa Winer
It happened to music and magazines. It's happening to television and movies. Now even mammography is going digital.
Within two years, the Food and Drug Administration is likely to approve new digital X-ray equipment to check for breast cancer, says Barbara Croft, a program director in the Diagnostic Imaging Program at the National Cancer Institute.
Advocates of the new equipment say it can locate cancerous tissue more precisely than existing equipment. In addition, it may be more accessible to women in rural areas.
In conventional mammography, X-rays pass through breast tissue and create an image on film. A radiologist then studies the image, looking for the smallest irregularities in pattern and density -- discrepancies that can be the size of a small grain of sand.
Conventional mammography works well, says Dr. Stephen Feig, professor of radiology at Jefferson Medical College in Philadelphia. According to Feig, women who are screened using conventional means reduce their risk of dying from breast cancer by at least 30 percent.
In digital mammography, no film is used. Instead, an image is created electronically, and it can be manipulated. Of particular interest to radiologists is the ability to "stretch the gray scale" -- to emphasize contrasts. This allows a radiologist to catch abnormalities that wouldn't show up on film, Croft says.
Exactly how much that advantage will contribute to finding small cancers or reducing the number of women called back for further testing is unknown, says Dr. Robert Smith, director of cancer screening at the American Cancer Society. He and other radiologists are optimistic that there will be pluses to this approach, but they say that digital mammography has not yet been proven to be superior to conventional mammography.
Offering access to hard-to-reach women
According to Smith, digital mammography offers advantages for screening women in rural areas. To avoid traveling long distances to clinics or hospitals with screening facilities, rural women have relied on mobile mammography units. But with conventional mobile mammography units, the film degrades if it is not developed right away. A digital mammography unit, on the other hand, could be kept away from home base for longer periods, because there would be no need to return to develop film.
In addition, a digital mammogram could be read immediately and women could be advised then and there whether more tests were needed.
But Smith wonders who would pay for digital mobile units. "Sometimes it is very difficult to bring the most basic services" to rural women, he says. Many hospitals lose money on conventional mammography because reimbursement from health insurers and Medicare doesn't cover their costs, says Feig. Digital mammography units, he says, can cost four to five times more than conventional mammography units, which run about $80,000.
While the benefits of digital mammography are being debated, researchers are inventing even more sophisticated tools for detecting breast cancer. Future mammography equipment might use electricity and lasers; biochemical markers may be able to detect cancer so early that surgery won't be needed. For now, though, old-fashioned film mammography and regular examinations offer women their best chance of catching breast cancer in its early stages.
Copyright 1999 WebMD, Inc. All rights reserved.
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