Digital mammography hits mainstream use

April 1, 2007

With popular actresses Sally Field and Andie MacDowell looking on, Dr. Etta Pisano picked up a Ladies Home Journal Health Breakthrough award last year, in recognition of her work in promoting better screening for breast cancer.

With popular actresses Sally Field and Andie MacDowell looking on, Dr. Etta Pisano picked up a Ladies Home Journal Health Breakthrough award last year, in recognition of her work in promoting better screening for breast cancer. Pisano, a professor of radiology and biomedical engineering at the University of North Carolina, was principal investigator in the Digital Mammography Imaging Screening Trial, a multicenter study of almost 50,000 women.

The Ladies Home Journal event was a landmark for radiology, and mammography in particular, publicizing the role of imaging in detecting and managing a high-profile disease. It also led to stories in the mainstream media that are sending a strong message to the general public: Digital can mean the difference between life and death for some women, particularly those with dense breasts.

That message has not been lost on U.S. women of screening age. More and more, breast imagers report that women are asking about digital mammography, feeding a shift that is bringing the digital modality well into the mainstream.

One person who has seen the effects of this shift is Gerald Kolb, chief development officer at Solis Women's Health in Austin, Texas.

"Some of our patients were requesting their films, and we started asking them what they needed them for. Enough of them said they were going to a facility that offered digital to get us concerned," Kolb said.

In fact, the DMIST that led to Pisano's award did not support digital mammography as strongly as some of its supporters would have liked. The study found that digital mammography is superior in women who are under age 50, are pre- or perimenopausal, or have dense breast tissue (NEJM 2005;353(17):1773-1783). Performance across the general population was similar to that of screen-film mammography.

A new study from the Ontario Cancer Institute underscored the implications of the DMIST results, however. The research, published in January 2007, also in The New England Journal of Medicine, found a strong connection between dense tissue and breast cancer (NEJM 2007;356:227-36).

"We have always worried about breast density. Certainly, the [Canadian] study provides food for thought, because according to DMIST, digital offers better performance for women with dense breasts," said Dr. Stamatia Destounis, a radiologist at the Elizabeth Wende Breast Clinic in Rochester, NY.

The research is compelling, but digital conversion is expensive and mammography providers face formidable challenges, including low reimbursement, high malpractice risks, and staff and specialist shortages.

Still, the trend toward digital seems clear.

"The whole radiology department is now digital except for mammography. It's crazy for mammography not to be digital. The only reason not to be digital is that it is too expensive-and it is expensive," said Dr. Daniel Kopans, a professor of radiology at Harvard Medical School.

GONE DIGITAL

The number of certified facilities with full-field digital mammography (FFDM) nearly doubled from 865 (9% of all facilities) in February 2006 to 1547 (17.6%) in February 2007, according to the FDA. During that period, the number of accredited digital units rose from 1210 (8% of mammography units) to 2244 (16%) (see graph).

From 2003 to 2005, the number of screening and diagnostic film mammograms in Medicare beneficiaries dropped from 6.62 million to 6.44 million, while the number of digital studies nearly tripled, albeit from a small base, from 265,000 to 760,000, according to Dr. David Levin, emeritus chair of radiology at Jefferson Medical College and Thomas Jefferson University in Philadelphia.

A recent survey of members of the Society of Breast Imaging found that almost half were performing digital mammography. Of those who were still wholly film-based, 77% planned to offer digital in the future. These newcomers will be able to learn from the experiences of early adopters, some of whom have been fully digital for several years.

"Our group has aimed to stay on the forefront of technology. When the time came to replace analog equipment, we thought digital was on its way," said Dr. Debra Mitchell, director of Breast Imaging of Oklahoma, which has been digital for six years.

The University of North Carolina at Chapel Hill worked with research systems during the DMIST and embarked on a full film-to-digital switchover only after the results became available in 2005.

Early adopters often view digital mammography as a step toward new technologies now in the research stage, such as contrast-enhanced digital mammography and tomosynthesis. Mobility is also an attraction. The two largest digital mammography vendors-Hologic and GE Healthcare-had 14 mobile digital sites in the U.S. as of February 2007.

The Comprehensive Breast Center in Seattle, part of the Swedish Medical Center group, runs a mobile digital mammography van service between facilities and also to remote rural areas. Real-time workup of patients is sometimes performed, but most digital studies are read in batches for the sake of efficiency, said Dr. Mary Kelly, a radiologist at the center.

TECHNOLOGY OPTIONS

Most FFDM systems feature flat-panel detectors based on amorphous selenium or amorphous silicon that translate x-rays directly into digital images. Three vendors offer this type of system: Hologic, GE, and Siemens.

With computed radiography, a reusable phosphorescent plate replaces the film cassette in a conventional analog mammography unit. The technologist places the plate into a processing unit, where it is scanned by a laser and developed into a digital image. No darkroom is needed. Processing units are available for single or multiple plates. As of February 2007, Fujifilm was the only company with an FDA-approved CR product.

Purchase prices for flat-panel units have dropped by only about 6% since 2000 and now range from $320,000 to $375,000, according to MD Buyline, a physicians' purchasing consultancy in Dallas. Most buyers also want to purchase computer-aided detection software, which adds about $50,000 to the price. CAD plays a more important role after digital conversion, as the need to put films through a digitizer has been eliminated. Instead, CAD marks appear at the push of a button on a workstation.

Digital CR cassettes cost from $750 to $1800, while the street prices for single-plate and multiplate CR processing units are about $140,000 and $240,000, respectively, according to MD Buyline. On top of equipment costs, upfront expenses include workstations, digital quality control, upgrades for the wireless network, long-term image storage, and a disaster recovery solution.

Facilities need to ask whether they can afford the up-front costs in light of future savings, Destounis said. Elimination of film and film processing yields some product and staffing savings, for example, and throughput is higher so fewer units are needed. Reimbursement varies, but many sources report higher rates for digital.

One way to manage acquisition costs is to convert gradually. But this approach is difficult, and most early adopters advise against it if possible (see accompanying article).

"No one should think that because we now have digital that film is no good. Film mammography has advanced over the last 20 years to the point where it is an outstanding technology. But it is difficult to coexist in the same center with digital," Kolb said.

The Elizabeth Wende Clinic has 13 x-ray rooms, including four with digital mammography systems from GE, Hologic, and Siemens.

"We are doing a little bit at a time to offset the cost. In a perfect world, you would convert all at once. If you have funding, that is the smartest thing to do. If the funding is not there and you need to convert slowly, it will be a painful transition," Destounis said.

Staff members direct patients with dense breasts to the digital units. The facility's PACS workstations allow viewing of images from the various vendors.

The Comprehensive Breast Center in Seattle obtained funding for flat-panel detector systems through the philanthropic arm of its multicenter medical group.

"It's really important for not-for-profit hospitals to use philanthropy, because capital is always short and there is never enough money for all needs identified. We relied heavily on charitable fundraising to get our digital mammography program going," Kelly said.

CR OPTION

The CR route represents a lower cost option for some centers, relative to acquisition of flat-panel detector systems.

"CR allows a first step into the digital world. Those who can't afford [flat-panel detector systems] may start out with CR," said Kevin Hodges, an analyst with MD Buyline.

The University of North Carolina has opted to use a mix of technologies. For high-volume screening, it is converting from analog to digital using CR.

"For a screening center, it makes sense to have a CR unit. You get more bang for the buck," Kuzmiak said.

UNC has opted to install flat-panel detector units in its diagnostic facilities, to allow immediate acquisition, thereby facilitating mammographically guided procedures.

"These units offer faster acquisition and display. In a diagnostic center where you have a lot of patients coming in for additional procedures, it speeds patient throughput," she said.

At Kelly's center, where both screen-film and flat-panel FFDM systems are operating, wire localization procedures are done exclusively on the digital equipment. It takes about a half-hour to perform these uncomfortable procedures on analog units, whereas digital takes only 10 minutes.

"Wire localization procedures are done almost in real-time now," Kelly said.

IMAGE SIZE MATTERS

Prospective buyers need to consider image size as well, according to Dr. Michael Trambert, lead radiologist for PACS reengineering at the Cottage Health System and the Sansum-Santa Barbara Medical Foundation Clinic in California. Lossy compression is acceptable in other modalities but currently prohibited for mammography by the FDA. And mammography providers will need 100% recall of prior images.

Image resolution varies, depending on the equipment, from 50-micron to 100-micron pixels. A 50-micron image contains approximately twice the information as a 70-micron image and four times the information of a 100-micron image. The Fujifilm CR system features resolution of 50 micron. The flat-panel detector systems from GE feature 100 micron, while Hologic and Siemens units feature 70 micron.

Higher resolution results in bigger data files. Noncompressed images using a large field of capture, for example, have the following data file sizes:

  • GE Senograph Essential: 14 MB

  • Hologic Selenia and Siemens Mammomat Novation DR: 26 MB

  • Fuji Medical Systems ClearView-CS: 53.5 MB

Trambert notes that the largest size images have the potential to dramatically increase storage costs along with hiking image interpretation and transmission times. It can prove very difficult to look at 50-micron images of large breasts for microcalcifications at full resolution, Trambert said. (For more information, see Trambert's article in this month's issue of Seminars in Breast Disease.)

Lower radiologist productivity in digital mammography has been documented in a number of studies, including one by Berns et al in the American Journal of Roentgenology (AJR 2006;187:38-41). That study found that it took twice as long to read a digital study compared with screen-film.

"In the whole chain of events in mammography, the most expensive resource is the radiologist interpreting the mammogram. If everything is good, but the radiologist is slow and nonproductive, you are not there yet," Trambert said.

Trambert advises providers not to purchase systems with the highest resolution unless they believe the images are truly better or they have fairly new analog units and CR becomes a good short-term option.

Kolb strongly disagrees, arguing that the increase in resolution allows better visualization of tiny microcalcifications and other details.

"Yes, the image is larger, and it may take a few seconds longer to review an image for a patient with particularly large breasts, but since when is the object to sacrifice image quality for interpretive time? Our physicians particularly like the clarity of the 50-micron image and the ability it gives them to truly characterize microcalcifications based on their shape. This is possible in most cases without going to magnification because of the 50-micron size," Kolb said.

CULTURE SHOCK

Radiologists who work at a much slower pace on digital may become frustrated, according to most early adopters. One of the toughest issues in converting from film to digital is getting radiologists on board and comfortable with soft-copy interpretation, sites report.

Digital mammography allows users to make many more manipulations to improve image quality, and this takes longer. Areas that look suspicious on analog look even more suspicious on digital studies, so a tendency for excessive recalls may be a problem in the beginning, Mitchell said. Radiologists might have to read several hundred mammograms to transform their basic impression of how a mammogram ought to look.

Administrators need to allow radiologists sufficient time to learn how to use the workstation at the front end of digital conversion. It is wise to spend a day training with vendor representatives, then arrange another training session on a future date to allow radiologists to air concerns and complaints, Mitchell said.

"The frustration of not knowing how to use the workstation can color the entire opinion about digital," she said.

After approximately six months, most radiologists are better adjusted and able to interpret images more quickly, but they are still likely to be slower than in the analog world.

SOCIAL BUTTERFLIES

Meanwhile, technologists have become much more productive. Screen-film screening exams lasted a half-hour, whereas digital studies can be performed in 10 to 15 minutes. Some are pushing for even faster exams.

"Our tech had no prior experience with digital, and we were producing eight-minute mammograms on the first day," Kolb said.

One of Kolb's centers is running two-thirds the number of units needed in film-based centers, but the systems will be doing one and a half times the volume of work. Staff aim to schedule 50 mammograms per unit per day and tend to overbook to compensate for no-shows.

In the screen-film world, however, technologists had more opportunities to interact with colleagues as they transported film cassettes and waited for processing. In the digital environment, they remain in one room and work at a faster clip.

"This a big change for the technologists, and you have to anticipate issues with it," Kolb said.

It may be wise to create new social opportunities to maintain morale. Since screening is busy and can be stressful, it is a good idea to switch techs from screening to diagnostic in the same day to allow more variety and to ensure that their experience with new technology is not too onerous or negative, Kolb said.

Mitchell warned that providers should do their homework on workflow change.

"There are plenty of facilities out there with experience in digital mammography, and it is really worth the effort to see how people have set up their practices and how the flow is designed," she said.

The Women's Diagnostic of Texas centers plan to book screening patients in half-hour blocks to ensure the system is running at full capacity. Patients will undress at their own pace and wait in their gowns in a room adjacent to the screening room. Then they will be seen on a first-come, first-served basis within their half-hour block.

Office layout changes include elimination of the darkroom and development of a larger reading room to accommodate workstations, said Dr. Kamilia Kozlowski, clinical breast radiologist and CEO of the totally digital Knoxville Comprehensive Breast Center in Tennessee.

DIGNOSTIC DIFFERENCES

The impact of digital on diagnostic mammography is very different from the screening setting, Kozlowski said.

"If your center does a lot of diagnostics in a day, you need to organize your scheduling better because the techs get patients through a lot more quickly," she said. "You could wind up with a waiting room full of diagnostic patients who have had mammograms and are waiting for follow-up studies, but the radiologists are not working at a faster pace."

Kozlowski strongly believes in the importance of demonstrating image findings to patients. When making the conversion, her center invested in monitors for the patient exam rooms. A low-cost web-based solution allows transmission of images for patient viewing.

It is also extremely useful to have a web-based solution for referring physician review, according to Trambert. An enterprise-wide PACS enables efficient communication between various departments in the hospital setting and among affiliated facilities. As with any area of radiology, it is best to involve a PACS consultant early on in the conversion planning process and develop a robust network for transmitting and storing images.

There are pros and cons of dedicated mammography PACS versus an integrated solution with the enterprise PACS. Generalized PACS workstations are often better for those who want to incorporate MRI and nuclear medicine, Trambert said.

Emily Hayes is feature editor for Diagnostic Imaging.

Early digital mammography adopters urge total conversion

Maintaining both film and digital imaging systems often proves difficult and inefficient

The most important advice for digital newcomers from early adopters is to go for a complete rather than gradual conversion, if financially possible. They cited the following reasons:

  • Maintaining both systems is a nuisance. You wind up with two separate infrastructures, one for film and one for digital, which is inefficient.

  • It's confusing for a doctor to read in a film-based environment and then switch to digital.

  • Technologists prefer digital and will fight to work on the digital systems.

  • Maintaining quality control on less used film-based units becomes more onerous.

  • Patients may prefer digital and sometimes compare notes. They don't take well to unequal treatment.

  • Making a partial conversion just delays the inevitable switch to digital. -EH