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While full-breast digital mammography continues to garner attention in medical meetings and technical conversations, screen-film mammography remains the industry's bread and butter technology-at least for the moment. Although digital technology has
While full-breast digital mammography continues to garner attention in medical meetings and technical conversations, screen-film mammography remains the industry's bread and butter technology-at least for the moment. Although digital technology has grabbed the limelight for the past several years, technical and socioeconomic challenges continue to keep this technology out of the driver's seat.
"With available technology today, digital breast imaging just isn't an economically viable alternative," said Donald Blomstrom, vice president of mammography in the U.S. for Instrumentarium Imaging.
Digital mammography technology still has several inherent shortcomings, according to Blomstrom. Digital detectors cannot produce the spatial resolution that film offers; light boxes used to view film are brighter and less expensive than most electronic displays; and film images, although bulky, are often easier to transfer, at least from one room to another, than large digital image files. Then there is the price of digital mammography products, which could be the most difficult challenge to overcome.
"Digital systems can cost around $400,000," said Joel E. Gray, vice president of business development and clinical systems for Lorad. "There are 10,000 facilities out there, and I'd say that 10% to 20% at the most could even consider the possibility of (going) digital because of its high cost."
Staff at facilities that do add digital equipment will have to determine which patients to image on digital equipment and which will be examined on film-based systems. Also to be decided will be whether to levy a premium charge for exams conducted with digital rather than analog technology.
Screen-film's hold on the market has been strengthened by a continuing stream of improvements made over the past several years. This R&D strategy is not likely to change anytime soon.
"I look at screen-film as strong and being around for at least 10 years," Gray said.
Efforts to improve screen-film mammography have been concentrated on enhancing ease of use and patient comfort. While Instrumentarium has been developing its Diamond digital system, for example, the company has refined its frontline Performa analog system with better compression for improved image quality and improved ergonomics aimed at increasing productivity.
The Performa, Siemens' analog Nova system, and those of other manufacturers provide consistently outstanding images, according to the companies, a claim verified by some clinical users. Dr. Stephen Feig, a professor of radiology at Mt. Sinai Medical Center in New York City, is confident that screen-film systems can perform a valuable service, although he notes that their performance is far from ideal.
"With screen-film systems we can find many cancers before they're a threat-but not most," Feig said.
Analog has its own serious drawbacks. One is the nature of film images. Because a hard copy is a final product, neither the density nor contrast in film images can be adjusted for better viewing. These constraints limit the clinical value of analog systems, according to Feig.
"Digital has the potential to do better," he said.
Gray agreed. Digital techniques, including image enhancement and computer-aided detection (CAD), might allow the identification of breast cancers only a few cells in size, he said.
"If you can identify and target cancers at a very early stage, you stand a much better chance of curing the patient," Gray said.
Analog systems might be better equipped to compete with digital equipment if improvements in film could be achieved. But major breakthroughs are not likely to occur in the near future, according to Arthur G. Haus, former director of medical physics for Kodak.
"For screen-film to make a huge improvement would probably cost a lot of money," Haus said. "For instance, new phosphor technology that would improve image quality could be costly."
Meanwhile, hardware engineers are addressing other opportunities to improve the function of film-based systems. Siemens has outfitted its Nova to include a pivoting bucky designed to improve both patient throughput and user-friendliness. Other improvements include isocentric rotation, which eliminates the need to make height adjustments when moving the C-arm from one view to the next, and an automatic exposure control system that optimizes imaging with the newer screen-film combinations now on the market.
Ultimately, these efforts may only buy time for film-based systems. As analog technology strives to keep up, digital technology will advance even more, creating images far superior to those captured with film-based systems.
Dynamic imaging of contrast media, CAD analysis, and 3-D reconstructions are simply beyond the grasp of analog technology. Electronic file transfer is immediate; hard-copy film transfer is not. Even resolution may pull ahead. As the popularity of digital mammography grows and sales volume increases, prices will inevitably come down. And cost is an issue that is likely to recede even further over the years if increased payments are assigned to digital imaging. The future can be seen in other technologies that have gone through this process, Blomstrom said.
"Things that weren't technologically possible five years ago are fairly commonplace today," he said. "This world will eventually all go digital."
2/28/01, Issue # 1504, page 1.