The US Food and Drug Administration (FDA) has approved a new mammography technique that uses digital, or computerized, images instead of film X-rays to screen for breast cancer.

General Electric Medical Inc. won approval to market its digital imaging system after conducting a one-and-a-half year trial that showed digital mammography was as effective as traditional film mammography for detecting breast cancer.

While mammography is the best screening method available for breast cancer, it is not infallible. Mammograms miss five percent to 17% of cancers, quite a high percentage considering an estimated 25 million women per year get mammograms.

Ed Hendrick, PhD, principal investigator for the General Electric trial and research professor and director of breast imaging research at the Lynn Sage Comprehensive Breast Center at Northwestern University Medical School, believes digital mammography eventually will become the preferred method for breast cancer screening.

"The real advantage of the new technology is that radiologists will be able to manipulate images," he said. "With digital images, you can zoom in, magnify, change the contrast of the image or view it in slices. Hopefully, this will mean that fewer women will be called back to repeat the screening."

Another advantage is these digital images can be stored and sent electronically. "Mobile mammography units serving women in rural or remote areas can transmit mammograms to a medical center and have them read on the spot," said Robert Smith, PhD, director of cancer screening for the American Cancer Society (ACS). "And digital images can be stored on computer disks, which gives women the ability to archive their mammograms more easily over the years to help radiologists track possible anomalies."

So far, studies have not shown that digital imaging is better than film mammography at detecting tumors. Robert Doyle, at the FDA's Center for Devices and Radiological Health, points out that some cancers identified digitally were not detected by conventional film methods, and vice versa. This is why the FDA has been slow to grant approval for the equipment.

Each company applying for FDA approval to market digital imaging equipment has to demonstrate that the technique is at least as good at detecting tumors as the X-ray method. So far, a number of companies have applied for FDA approval, but only General Electric has received it.

From a patient's point of view, there is no difference between digital and film mammography in terms of procedure. The image just isn't recorded on film. While digital imaging is a less expensive method of processing images than film, the equipment itself is far more expensive, costing between $350,000 and $400,000 per machine.

Scientists believe digital imaging will open up new areas of research. "Digital mammography is a little like the MRI," said Dr. Hendrick. "When MRIs were first approved, they were found to offer better brain and spinal cord images than a CT scan. Now, after 15 years, we've extended their use to many other areas. The same thing will happen with digital mammography."

In the meantime, women shouldn't wait for the new technology to become widely available before getting their next mammogram. It will be some time before digital mammography is widely available. Besides, said Dr. Hendrick, "film screen mammography is quite good and getting better all the time."

The ACS recommends women age 40 and older have an annual mammogram, annual clinical breast examination by a health care professional, and perform monthly breast self-examination. Women ages 20 to 30 should have a clinical breast exam performed by a health care professional every three years and should perform monthly breast self-examination.