Vendors follow divergent strategies to fill digital void

Upgrades and enhancements for digital mammography systems are good news for women's health practitioners who have already invested in the next stage of mammography. But those still contemplating the move to digital technology are beginning to consider alternatives.

Early results from 3D tomosynthesis are beginning to come in from luminary sites, making the prospect of future clinical use more immediate. Prospective customers now are faced with the dilemma of choosing whether to wait until tomo is ready or going ahead with the current generation of digital mammography. Their choices are complicated by a third possibility, CR mammography, which is pending regulatory clearance but could be on the market within months.

There's no question that tomosynthesis has a certain "wow" factor. According to executives at Hologic, when they pulled up images in their RSNA booth on the company's work-in-progress tomosynthesis unit, the reaction was immediate and positive.

"Indications are that tomosynthesis will be better in many cases and equal to digital mammography in all other cases, and you will have fewer recalls," said James Culley, Ph.D., marketing manager for Hologic.

Preliminary clinical findings show that the Hologic's tomosynthesis system is superior to conventional mammography 33% of the time, equivalent 54%, and inferior 12%. But even when tomosynthesis was inferior to mammography, it still visualized the abnormality. It just didn't characterize the lesion well, according to Dr. Stephen Poplack, an associate professor of diagnostic radiology and obstetrics and gynecology at Dartmouth Hitchcock Medical Center.

The study, reported at the 2005 RSNA meeting, also demonstrated that digital breast tomosynthesis would have obviated many of the calls to patients to return for further workup. Approximately half (49 of 99) of the women would not have been recalled if tomosynthesis had been used in lieu of mammography, Poplack said.

Tomosynthesis has the potential to improve sensitivity in detecting breast abnormalities, particularly those that may be obscured by fibroglandular tissue. It can also visualize the margins of lesions to help physicians make better informed decisions about benignity and malignancy, said Vince Polkus, mammography advanced applications product manager for GE Healthcare.

In combination with contrast-enhanced imaging, digital breast tomosynthesis may be able to characterize the vascularity of breast lesions. A study tracing the initial experience with contrast-enhanced breast tomosynthesis using a GE system suggested that the technique produces the same kind of qualitative information about vascularity as MR. Results of the study were presented at the RSNA meeting.

Tomosynthesis units are still works-in-progress, however. The first proof-of-concept machines shown over the last few years are being replaced by more marketable products. These may provide buyers the option of doing tomosynthesis as well as mammography in a more conventional sense.

A prototype from Siemens Medical Systems is a modification of an existing Mimosa Notation digital imaging product. The prototype incorporates a motorized x-ray tube, which allows image projections of the breast to be acquired from different angles. Studies to find ways of improving the current technology and optimizing radiographic techniques to enhance image quality and reduce radiation dose are ongoing.

Other vendors are adapting their own digital systems. Hologic's Selenia breast tomosynthesis system is being optimized to perform 3D volumetric studies as well as regular mammography. GE's Senographe tomosynthesis machine is being adapted to support conventional studies.

"Where today the standard of care for screening involves looking at four images in an exam, with 3D volumetric imaging of the breast, radiologists will be looking at potentially several hundred thinner slices of the breast. It's mandatory to do this in a manner that will not negatively impact customer productivity," Polkus said.

Meanwhile, CR mammography is close to entering the U.S. market, as systems developed by Fujifilm Medical Systems, Agfa HealthCare, and Eastman Kodak make their way through clinical trials and FDA review.

The Fuji CR system for mammography (FCRm) is in the final stages of review by the FDA. FCRm includes software that allows the Imaging and Information Processor (IIP) technologist console and ClearView-CS multiplate CR reader used in general radiography to process digital mammography scans. FCRm increases spatial resolution by providing 50-micron pixel sampling. It increases detective quantum efficiency by 50% and reduces noise by 50% by obtaining information from both sides of the imaging plate.

Agfa Embrace CR mammography can be delivered on the same platform of digitizers used for general radiography. Connectivity is a distinguishing feature, said Pat Montgomery, manager of women's care.

"When you look at the mammography installations where CR may be going, there are a lot of reporting systems, patient scheduling systems, and CAD," she said. "All those elements need to be integrated into one system to give the kind of workflow that mammography departments need, especially in today's environment where there are shortages of technologists and radiologists. Agfa can bring that connectivity to the table."

The Kodak DirectView CR mammography feature, an upgrade to the company's general radiography systems, has increased image resolution and detective quantum efficiency and offers special cassettes for imaging breast tissue close to the chest wall.

Unlike tomosynthesis, which must be tailored to the real world of imaging, CR mammography can be slipped into imaging routines and follow the same general radiography procedures and workflow and use the same user interfaces.

With CR mammography installations in other parts of the world and a track record of versatility and cost-effectiveness, the technology has proven market acceptance. It may be just the ticket for imaging centers that can afford neither to wait nor to pay for 3D breast tomosynthesis.