Fine Tuning Digital Mammography

Digital mammography systems are striving to differentiate themselves in image quality, easy integration with CAD and the ability to more efficiently review and manage images digitally - and clinicians and market watchers hope the Digital Mammographic Imaging Screening Trial (DMIST) of 50,000 women at 35 sites will bring some answers when results are released next spring. In the meantime, a variety of facilities are successfully transitioning to digital mammography.

Full-field digital mammography (FFDM) came on the scene in 2000 with promises of better images, reduced radiation dose, boosts in productivity and more efficient image management. GE was first with its Senographe 2000D; Fischer and Hologic followed with SenoScan and Selenia respectively - with the combined market penetration of three vendors hovering between 5 and 10 percent. Siemens Medical Solutions is the newest to market with its Mammomat Novation gaining its PMA in August. (See "New Systems Crowd the Market," Page 30.) New digital mammography options from PlanMed and Sectra, and a CR-based mammography system from Fujifilm Medical Systems, are in the works and are expected to hit the market in the next year.

Despite all of the market action, digital mammography has not yet established its superiority over conventional analog products. But a more firm answer is expected next spring after researchers evaluate the results of the Digital Mammographic Imaging Screening Trial (DMIST), a comparison of digital and film mammography in nearly 50,000 women conducted at 35 clinical sites in the U.S. and Canada. "We believe this study will be powerful enough to tell if digital mammography is better, the same or worse than conventional mammography in an average risk population," says Etta D. Pisano, MD, DMIST principal investigator and professor of radiology and chief of breast imaging at the University of North Carolina School of Medicine at Chapel Hill.

Pisano says if the diagnostic accuracy of digital and conventional mammography proves to be the same, digital mammography may be justified if it can reduce the number of false positives or costs. As the DMIST trial winds down, sites that have implemented digital mammography are finding:

• An improved ability to resolve calcifications, which translates into reductions in the recall rate for calcifications.
• Streamlined CAD processes via the direct integration of CAD technology.
• The pluses of the digital environment: the ability to store and transfer images digitally.
• A hefty learning curve within mammography that can include workflow challenges and slight increases in the callback rate. FFDM sites do predict productivity gains after the transition to digital is complete.
• A need for a streamlined workstation to help integrate analog and digital technology, other breast imaging modalities and PACS.

THE DIGITAL EXPERIENCE

The transition from analog to digital mammography typically requires a somewhat lengthy learning curve. In fact, Bruce Schroeder, MD, director of breast imaging at Eastern Radiologists, Inc. (Greenville, N.C.), a Fischer SenoScan FFDM site, says it may take up to one year to fully re-train radiologists in digital reading. Jack Moss, MD, co-medical director of The St. Vincent Breast Center (Indianapolis), another Fischer sites, adds, "[The transition to digital mammography] is harder than transitioning to filmless than in other modalities. That's probably because we're able to see so much more information." The additional information available on a digital mammogram requires some adjustment on the part of the radiologist to determine if an abnormality is a cancer.

Mary M. Kelly, MD, medical director of imaging at the Providence Campus Comprehensive Breast Center of the Swedish Cancer Institute (Seattle), has been using a Hologic Selenia FFDM system for nearly a year. "In some cases, we can retrospectively see our digital findings [cancers] on older analog mammograms, but the finding was more obscure on the analog film," Kelly points out. "The whole idea is to push our accuracy as high as possible. Although it's a little too soon to tell whether our cancer detection rate is up, our recall rate is up a bit. We're hoping that the cancer detection rate will follow."

Eastern Radiologists also has seen slight increases in recall rates since installing digital. Schroeder points out that this phenomenon also occurs with a new analog system or when radiologists return from a conference. "Long-term, I suspect our recall rate will go down. In fact, we've already realized a significant decrease in our calcification recall rate," continues Schroeder. That's because digital technology provides additional magnified views that help radiologists determine how to proceed without a second study.

The Center for Breast Care (Deerfield, Fla.) installed a GE Senographe more than a year ago, and Medical Director of Breast Imaging and Intervention Kathy Shilling, MD, reports that the center is over the hump of the learning curve. She says, "We're not calling back any more patients with digital mammography. We're probably calling back fewer because there are so many tools on the digital monitor to evaluate the breast."

For certain populations, the clinical advantages of digital mammography are clear. Monte Clinton, administrative director of radiology at the Dartmouth-Hitchcock Medical Center in Lebanon, N.H., says, "Our Hologic Selenia provides much better images for certain subsets of patients-young patients with dense breasts and women with very large breasts."

DMIST results should resolve many of the remaining clinical questions. Moss concludes, "The idea is to find cancers as early as we can. We expect our callback rate will go down as radiologists master digital tools like magnifications, windowing and leveling and that the patients we do call back will have real findings that are smaller [than they would be on analog film] with a better prognosis."

PRODUCTIVITY, WORKFLOW & WORKSTATIONS

The outlook on productivity gains with digital mammography is positive, too. "We expect to find significant productivity gains," Clinton says. "We can see that it will be much faster than analog."

The process for techs is simple. Techs no longer need to handle cassettes or wait for film processing. In fact, QA can be completed while the tech remains in the room with the patient. St. Vincent Breast Center has seen technologist time in the room with patient drop from 15 to 20 minutes to four to five minutes since installing technologist workstations for each digital mammography room, thus allowing techs easy access to images and data.

For radiologists, however, the digital mammography workflow equation is not quite as straightforward. That's partially because radiologists need to conquer the awkwardness of comparing digital results with previous analog mammograms. "We need to devise a better way to hang mammograms," Moss explains. "This isn't necessarily a technology issue, but a question of structure and ergonomics."

Take for example Eastern Radiologists, where the radiologist sits in the center of a double bank digital workstation, an MRS Mammography Reporting System, an R2 ImageChecker monitor and an analog viewbox. "Everyone [vendors] has nice systems, but right now they don't talk to each other," Schroeder says. "It takes longer getting ready to read than it does to read. We need for one event [like calling up a digital case] to automatically trigger the other systems."

Moss of St. Vincent Breast Center looks forward to taking one small step in the workflow issue when the center installs a Cedara multi-modality workstation that will allow radiologists to see DICOM ultrasound and MRI images as well as FFDM images from any manufacturer on a single screen. Moss says the new monitor is the first step to the real workstation solution. He opines, "To some extent, digital can be slower because you're flipping back and forth between views, but we will get there as far as efficiency."

Shilling admits one of the hardest parts of transitioning to digital is setting up the reading room so that it is convenient to look at digital images next to film mammograms. The Center for Breast Care relies on an L-shaped arrangement with digital soft-copy reading stations on one side and film roller boards on the other.

The Providence Comprehensive Breast Center employs a similar approach. "Our set-up isn't the most elegant, but it works for us," Kelly says. Analog multi-panel viewers are at a right angle adjacent to digital monitors. Kelly and her colleagues read in batches, so clerks hang previous films to coincide with the digital list, eliminating any searching for films. "I begin by looking at previous mammograms for a gestalt of dense breast tissue, then look at multiple digital views and refer to analog to compare abnormalities or areas of asymmetry," Kelly explains. "The process is complete by flipping on CAD for review. The series of motions seems awkward at first, but we've gotten used to it."

Another plus of digital technology is the ability to seamlessly integrate CAD. Schroeder explains the process. "With analog mammography, we had to print out and scan the films before applying CAD. Now the process is streamlined and automated. R2's ImageChecker marks the unprocessed image data, which makes CAD even more valuable."

IMAGE STORAGE & MANAGEMENT

So what do sites need to do to maximize the potential of digital mammography? Implement soft-copy reading.

Schroeder admits, "When we first deployed digital mammography, we thought about hard-copy reading. But doing that is a mistake because then you're not reading all of the information that's on the digital mammogram."

Indeed, most digital sites read nearly exclusively soft-copy, which requires an FDA-approved display (see "Monitors Matter," Page 28.), storing natively on the workstations and some archive images on PACS. Film is printed minimally for referring clinicians or surgeons. Schroeder confirms, "We're eating about 10 gigabytes of storage a day, but storage is cheap."

The Swedish Hospital Breast Center relies on a Hologic MIMS mini-PACS. The system holds 86,000 studies, which are then available for immediately retrieval. In fact, MIMS allows electronic retrieval from anywhere within the four breast centers affiliated with Swedish Cancer Institute.

Shilling points out that the ability to move images across wires is a tremendous plus. The Center for Breast Care eased into digital mammography by installing the technology at a satellite clinic prior to main center. Digital mammograms are transmitted from the satellite to the main reading center via a T1 connection. Shilling says eliminating film processes and reading soft-copy images makes the mammographer more efficient.

Acquiring, storing and moving digital images can be a daunting proposition. Clinton advises, "Involve the IT department, and talk to the technical folks at the manufacturers. Make sure you have a sufficient network infrastructure to send the large datasets." Dartmouth's new remote imaging center will have a 1-gigabyte backbone to ensure rapid transfer.

LOOKING FORWARD

Within the next year, early adopters expect to iron out the digital wrinkles and add to the list of benefits and advantages. DMIST should answer questions about whether or not and how digital is superior to analog. And as digital sites get a leg up on the learning curve, they could report increased accuracy and productivity and enhanced care. True integration among systems may be a bit farther down the road, but will happen.

In the meantime, some experts are already considering the next steps. Gerald Kolb, president and CEO of Breast Health Management (Bend, Ore.), points out, "What we're really after is the digital image. Before long, we'll be able to use electronic technology to enhance digital mammograms and aid in interpretation. These tools aren't here yet, but it's coming."