According to a new study that will be published online today in the journal Radiology, not all modes of digital mammography are created equal.

Researchers from Prevention and Cancer Control at Cancer Care Ontario have found that digital direct radiography is significantly more effective than computed radiography at detecting breast cancer, says a press release from the Radiological Society of North America. The two modes are both kinds of digital mammography, which has become more popular over the years than film mammography, which uses x-ray film.

However, they differ in how the images are read. Direct radiography is an online system in which the detector is part of the mammography unit, and the image it generates is read and analyzed in real time, as the picture is generated, the press release says. Computed radiography, however, is an offline system — the detector is removable and an external device is used to read the image after it has been generated. And while it's generally known how digital mammography stacks up against film mammography for breast cancer detection, less is known about which digital mode is more effective, lead author Anna Chiarelli says the in the statement.

For this study, the researchers analyzed data from the Ontario Breast Screening Program. They identified 403,688 women who were screened by film mammography, 220,520 who had been screened with direct radiography, and 64,210 who had been screened with computed radiography, and followed them for 12 months. They found that direct radiography detected 4.9 cancers per 1,000 mammograms, comparable to film mammography's detection rate of 4.8 cancers per 1,000 mammograms, the Radiological Society says. Computed radiography was less effective however, detecting only 3.4 cancers per 1,000 mammograms.

"There may be several technical reasons reported by others for the lower effectiveness of CR, including loss of spatial resolution, or sharpness, and increased image noise, or granularity," Chiarelli says in the statement.

Source :Digital mammography cancer detection rates may vary significantly. EurekAlert website. Published May 14, 2013. Accessed May 14, 2013.