Digital Mammography Has Potential to Detect Small Tumors, Increase Accuracy in Dense Breasts

CHICAGO--Initial experience with a prototype digital mammographysystem indicates that the new technology has the potential todetect breast tumors much smaller in size than is possible withconventional mammography, and can be manipulated to explore areasof breast tissue that harbor occult cancer.

As a result of positive preliminary research results, full-scaleclinical trials of the digital mammography system will begin inthe next few months, Martin Yaffe, PhD, reported at the RadiologicalSociety of North America meeting.

In tests using contrast-detail and mammographic phantoms thatsimulate signs of cancer or other breast disease, as well as actualbreast scans from volunteers, the digital system has achievedspatial resolution of images as small as 1/20th of a millimeter.[Oncology News International's original report on Dr. Yaffe'sresearch (August, 1994) includes a digital phantom image.]

"In laboratory tests, we've seen smaller, more subtle structuresthan can be seen with conventional mammography," said Dr.Yaffe, senior scientist, Imaging Research Program, SunnybrookHealth Science Centre, and professor of radiology and medicalbiophysics, University of Toronto, Canada.

With special computer graphics techniques, the system has increasedthe clarity of images of dense breast tissue, which is difficultto screen for cancer mammographically, and it has enhanced thedepiction of fibers or deposits that often define the extent ofbreast cancer.

'Zoom in' for a Closer Look

"The image can be altered on the digital mammography systemto highlight an area where a cancer might be obscured by normaltissue because a woman has dense breasts," Dr. Yaffe said.The radiologist also can 'zoom in' for a closer look at microcalcificationsor other masses that are suspicious for cancer, he said.

The digital mammography unit does not use x-ray film. Rather,the device has electronic detectors that record the images producedwhen the breast is bombarded with x-rays and then translate theimage data into digital information.

The digital data are converted into an image that can be viewedon a computer screen, sent from one site to another, or storedand retrieved instantaneously.

Because of these advantages, the digital system may help to extendmam-mography screening capabilities to women who live in isolatedareas. "Digitized mammograms can be easily and quickly transmittedover phone lines or via satellite for consultation with radiologistswho are experts in the field," Dr. Yaffe said.

The system may facilitate screening and follow-up of individualsas well as large groups. "With digital mammog-raphy, a virtuallylimitless number of pictures can be stored and called up fromthe computer with the touch of a button. It also will be easierto compare a recent mammogram side-by-side with earlier studies,"he said. Such comparisons can help detect subtle changes in breasttissue that have taken place over time and might be early warningsigns of cancer.

Digital mammography may set the stage for computer-assisted diagnosis.One day, Dr. Yaffe suggested, "we'll be able to tell thecomputer to analyze mammograms, pointing out the areas that aresuspicious for cancer or recognizing patterns that may suggesta cancer will develop in the future."