The Low-down on Digital Mammography Displays
Choice is a new addition to digital mammography displays and workstations with the recent addition of third-party, high-resolution monitors and PACS. But buyer beware when it comes to DICOM compatibility issues between acquisition devices and displays. A good QA plan also is key, along with making sure your reading room is digital mammo-friendly. Here are some tried-and-true tips to getting it right.
Until recently, digital mammography system buyers had little choice in display systems; each mammography vendor selected a display for use with its acquisition device and reading station and submitted a soup-to-nuts package to the FDA for approval. That meant each workstation and display worked with just one vendor's system. But those days are history.
"The market is changing rapidly and giving buyers more choice in the display systems used to view digital mammograms," explains Margarita Zuley, MD, radiologist with Elizabeth Wende Breast Clinic (Rochester, N.Y.).
The changes have been spurred by recent FDA approvals for third-party PACS and high-resolution displays for presentation of digital mammography images. Consequently, digital mammography is becoming more of an a la carte purchase with sites able to customize a solution by selecting a preferred or best-of-breed acquisition device, soft-copy review stations and PACS workstations.
The buyers' market that began last year as digital mammo displays started gaining FDA clearance brings a few challenges. For starters, DICOM incompatibilities between digital mammography acquisition devices and displays still exist and can cause subtle image degradation. Vendors could remedy remaining DICOM issues by this summer, industry watchers say. Nevertheless, a thorough test drive pairing potential acquisition systems with displays is warranted, says Zuley. After installation, sites need to implement processes and solutions to maintain high image quality. This includes implementing a QA program and fine-tuning the reading room environment for digital image review.
Other changes are in the works, too. Flat-panel displays for digital mammography are right around the corner. This affects current sites eyeing the replacement market and new installs that need to prep for the brave new world of flat-panels.
Buying power
Whether an imaging facility buys an entire digital mammography system or purchases individual components, image quality of the display should serve as the basis of the final product evaluation, says Capt. Jerry Thomas, radiological physicist with Bethesda Naval Hospital (Bethesda, Md.). Maria Kallerghi, PhD, program leader, digital medical imaging at Moffitt Cancer Center (Tampa, Fla.), adds, "Right now, it's not as much a matter of CRTs vs. flat-panels. Image equality is the most important factor."
Radiologists should evaluate various displays and determine how each shows calcifications and masses. Other evaluation factors include the user interface, which can enhance or detract from a display. A busy, bright interface can make reading more difficult. Radiologists should analyze soft-copy hanging protocols and ensure that they support workflow.
Buyers brave enough to customize a solution can overcome DICOM incompatibilities by conducting a side-by-side comparison of images on the vendor's mammography workstation to images on the soft-copy review station, looking for minor degradations, Zuley says.
Nikunj Patel, MD, director of high-tech imaging at Scripps Clinic (La Jolla, Calif.), adds a few more criteria to the pot. Buyers must make sure that a display has adequate resolution to support digital mammography. Palette is the next consideration, with more bits translating into more shades of gray per pixel. Then, Patel says, the decision can be based on a consensus of personal preferences among radiologists. This includes items like anti-reflective glass, blue or gray tinted screens and self-calibration software. It is important to stick with a single display system for digital mammography across a site, as a hodge-podge approach can affect consistency among reads, Patel concludes.
Another digital mammography display purchase issue is the service contract. Buyers need to understand each party's responsibility if a monitor fails. Moffitt Cancer Center placed an upgrade clause in its digital mammography service contract; when the mammography vendor integrates flat-panels, the Center will receive flat-panel upgrades on its workstations.
The QA question
While image quality and interfaces are important considerations, there are other decision-making criteria. Buyers need to be informed about the manufacturer's recommended QA program and understand the amount of time required to perform all QA tasks associated with the display. "There are QA differences among manufacturers," Thomas notes. "QA can be a substantial time commitment." Kallerghi adds, "Buyers need protocols so they know when and how a monitor fails."
At Moffitt Cancer Center, radiologists are required to complete a SEMPTE test every day before reading digital mammograms. "If users don't check every day, problems can creep up," explains Kallerghi. Any problems are immediately reported to the vendor, with the service contract providing for a next-day replacement.
After a digital mammography system and display are selected, buyers can maximize image quality by adjusting the reading environment. "It's possible to make a very good display look horrible or transform an average display into a very good one by changing the reading environment," says Thomas.
The analog-digital comparison issue can be an ergonomic nightmare with radiologists in poorly designed rooms forced to twist and turn to complete comparisons. Such contortions can be avoided by placing the viewbox parallel to the digital workstation. Other best practices for reading digital images center around lighting. Indirect lighting is advisable; overhead or hall lights that shine on the display can reduce the radiologist's ability to see fine details on the mammogram.
The advent of flat-panels
A number of display vendors are securing FDA approval of flat-panel monitors for digital mammography. Although digital mammography vendors have not yet integrated flat-panel displays into their systems, the industry is moving in that direction. The smooth new flat-panels are an option for PACS workstations. Moreover, early adopters of digital mammography will soon find themselves in the market for replacement displays as the lifespan of CRTs is just about three years.
Flat-panels bring a number of advantages to digital mammography display. "The single biggest advantage is the elimination of veiling glare. This results in a sharper image. Flat-panels and CRTs are about equal in their ability to display calcifications, but flat-panels do an excellent job of displaying masses," opines Thomas. Flat-panels tend to be a bit larger than CRTs, so radiologists are able to view slightly larger images. Finally, the slim systems take up less real estate on the desktop and last longer than their CRT counterparts.
The primary hitch with flat-panels comes in the oh-so-familiar territory of calibration. Flat-panels must be appropriately calibrated so that they don't lose just-noticeable differences between shades of gray. Calibration can be tricky and typically entails more than 256 calibration points and may require additional shades of gray or pseudo-grays. Is flat-panel calibration complicated? Yes. Do end-users consistently follow through with recommended calibration? No.
"Display vendors have recognized this major weakness in end-users. Their answer is to remove the end-user from the calibration equation by including self-calibration features that eliminate a lot of flat-panel QA," confirms Thomas.
Handy calibration tools include a simple red light-green light scheme that warns the radiologist when a display is out of calibration. Kallerghi notes, "If luminance is off, the human eye can adapt to problems." Automated warnings correct for this factor. Another plus for radiologists weary of daily SEMPTE tests? New automatic calibration tools handle this chore. Although medical physicists won't be able to completely dispense with the puck (or photometer) used for on-site calibration tasks, many display vendors now offer remote calibration.
Conclusion
Choice can be a dizzying proposition, but ultimately it is a positive force in the market. In the digital mammography world, buyers will soon be able to optimize a solution to meet their needs. This requires some homework on the display end. The side-by-side comparison of review stations connected to the acquisition systems under consideration is crucial and will guide the facility toward a final purchase that optimizes image presentation. Understanding and adhering to recommended calibration options and processes - particularly as flat-panels hit the market - is another important factor in the digital scene. Outside of the display system, buyers can enhance image viewing by creating a reading environment geared to the specific needs of digital mammography. The end result will be a solution and environment primed for digital mammography reading, which enables the facility to meet the holy grail of the healthcare business: maximum productivity and improved patient care.
DIGITAL MAMMOGRAPHY DISPLAYS AT A GLANCE
Health Imaging & IT takes a closer look at the specifications of digital mammography display systems on the market.
Vendor: Barco Medical Imaging Systems
Display: Coronis Mammo 5MP (MFDG 5621)
Screen technology: TFT AMLCD dual domain
Resolution (pixels): 2560 x 2048 / 2048 x 2560
Screen size: 21.3"
Viewing angle: 170º
Contrast ratio: 900:1 without PPU; 700:1 with PPU
Luminance: 600 cd/m2 calibrated, > 800cd/m2 maximum
Palette: 1024 shades of gray from a palette of 4,096 shades
Other: Stabilization, calibration and automatic QA provided by embedded patent-pending I-Guard software.
Vendor: Double Black Imaging
Product name: IF2105M
Screen Technology: LCD
Resolution (pixels): 2048 x 2560 rotatable portrait to landscape
Screen size: 21.3"
Viewing Angle: 170º
Contrast ratio: 600:1 (typical)
Luminance: 750 cd/m2
Palette: 10-bit
Other: The IF2105 features a bonded protective panel and offers retractable front sensors for auto-calibration. The local workstation software allows individual workstations to be auto-calibrated without network software.
Vendor: Eizo Nanao Technologies Inc.
Product name: RadiForce G51
Screen Technology: LCD
Resolution (pixels): 2560 x 2048 (landscape); 2048 x 2560 (portrait)
Screen size: 21.3"
Viewing Angle: 170º
Contrast ratio: 600:1
Luminance: 700cd/m2
Palette: 1,024 grayscale tones from a palette of 3,061
Other: Clear and blue base LCD types available, DICOM calibration support, FDA 510(k) compliant, USB.
Vendor: Image Systems Corp.
Product name: FP2130M
Screen Technology: LCD
Resolution (pixels): 2048 x 2560
Screen size: 21.3"
Viewing Angle: 170º
Contrast ratio: 600:1 typical
Luminance: 750 cd/m2 maximum
Palette: 10-bit grayscale
Other relevant information: FDA approval pending, hands-free, auto calibration, local (automatically included) and network versions of calibration software available.
Vendor: National Display Systems
Product name: AXIS V
Screen Technology: AM-LCD, Dual Domain in Plane Switching (DIPS)
Resolution (pixels): 2048 x 2560
Screen size: 21.3"
Viewing Angle: 170º
Contrast ratio: 800:1 typical
Luminance: 750cd/m2 maximum
Palette: 3062 net from 12-bits
Other: The AXIS Series has remote connectivity over a network (USB from PC to panel, daisy chained together). Optional Integrity Networking Software is an integrated display quality management system.
Vendor: Planar Systems
Product name: Dome C5i
Screen Technology: LCD
Resolution (pixels): 2048 x 2560 (portrait) or 2560 x 2048 (landscape)
Screen size: 21.3"
Viewing Angle: 170º
Contrast ratio: 600:1 typical
Luminance: 700 cd/m2 or 200 fL typical
Palette: 3,061 unique shades of gray
Other: The Dome C5i comes with Dome CXtra CX Edition monitoring and calibration software. Dome CXtra CX Edition ensures that Dome CX displays conform to DICOM standards.
Vendor: Siemens Display Technologies
Product name: SMD21500
Screen Technology: LCD
Resolution (pixels): 2048 x 2560
Screen size: 21.3"
Viewing Angle: 170º
Contrast ratio: 600:1
Luminance: 700 cd/m2 or 205 fL typical
Palette: 1536 Shades (256 displayed)
Other: Utilizes Planon backlight, which allows for life expectancy up to 100,000 hours and immediate start-up from sleep mode. SMfit ACT calibration software and remote access packages are sold separately.
Vendor: US Electronics
Product name: ME511L
Screen Technology: LCD
Resolution (pixels): 2000 x 2500
Screen size: 21.3"
Viewing Angle: 170º
Contrast ratio: 600:1
Luminance: 750 cd/m2 maximum
Palette: 11-bit (2048 grayscale)
Other: All monitors are ready for remote monitoring and performance evaluation. The company plans to introduce Front Sensor Mammography 5 Mega Pixel display to monitor continuously the display DICOM performance.