Digital mammography creates new opportunities in cancer detection

Digital offers clear logistical advantages, such as the ability to integrate mammography images and reports with the rest of the digital radiology enterprise. And all major trials completed to date have concluded that clinically, digital is at least equivalent to, if not statistically better than, screen-film. With the high spatial resolution so critical for detecting masses and microcalcifications, film has long been the standard for breast cancer screening. But the current crop of FDA-approved digital mammography systems from Fischer Imaging, GE, Hologic, and now Siemens has improved markedly over the prototype devices prior studies were based on. New digital systems, for example, demonstrate improved depiction of low-contrast objects in contrast-detail studies and a wider dynamic range. Both attributes are expected to bolster the diagnostic quality of images acquired in dense breasts. Advances in soft-copy display features have honed the rough edges of early digital workstations that were less intuitive than those available today. More intriguing than the digital versus film debate, however, is the opportunity that digital represents in terms of tomography and contrast subtraction applications. The advent of digital detectors has paved a new road for x-ray mammography that many considered beyond improvement. From scientific papers to plenary sessions and update courses, the RSNA meeting in December offered a plethora of data on the clinical, socioeconomic, and practical aspects of digital mammography. Dr. Daniel Kopans, chief of breast imaging at Massachusetts General Hospital, offered a succinct summation of digital's status. "Digital mammography is probably going to replace screen-film mammography, and for many of us it already has," he said. "Others are likely to stick to screen-film until studies show that digital is actually better-and that's fine." CAPITAL ASSETS When and if that determination will occur remains to be seen. Digital's clinical contribution to cancer detection is a topic researchers have tried to define since its introduction as a prototype technology in 1996. Amid numerous smaller efforts, two major studies have been conducted to date: One took place in the U.S. in 2002, and another in Norway was recently completed. A third study, the Digital Mammography Imaging Screening Trial (DMIST), is in the final stages of data collection, with results expected to be published this spring. All have focused exclusively on comparing clinical attributes of digital mammography versus screen-film. The 2002 study, sponsored by the U.S. Department of Defense, used a prototype system developed by GE. The paired study involved 6736 women. Final results were reported by Dr. John Lewin, an assistant professor of radiology at the University of Colorado Health Sciences Center (AJR 2002:179;[3]:671-677). Screen-film and digital mammography scans were interpreted independently. No significant difference in cancer detection was found between the two techniques, although digital mammography resulted in fewer recalls, a trend that has been repeated in similar, smaller studies.