Managing Digital X-rays

The mantra of all healthcare facilities - large, mid-size and small - is to deliver the best patient care possible. Near-immediate access to the latest, most accurate information and patient images is one of the very fine lines in radiology departments that can result in success or failure to achieve that goal.

Managing digital x-rays efficiently and maximizing productivity is among healthcare facilities' top priorities. Ask a radiologist or a hospital IT manager how to do it, and, more often than not, the first response is to plan the initiative correctly from the beginning.

DR: The Specs That Matter

There are many different technologies, features, benefits and potential disadvantages to consider when purchasing a digital radiography (DR) system. Here are some key factors to consider.

Detector technology

There are three basic types of systems in digital radiography (DR) - CCD-based (charged-couple device) technology, direct flat-panel detectors and indirect flat-panel detectors.

CCD-based detectors use minification optics to minimize large radiographic images to a size more appropriate for CCD detectors. Most systems use multiple CCDs, so the individual images are "stitched together" through image processing to produce a smooth final image.

The distinction between direct and indirect flat-panel technology is whether x-rays are converted directly into electrical energy (or electron whole pairs) or whether x-rays first are converted into optical light and then converted into electron whole pairs.


DR system price tags can easily reach the seven-figure range with additional options, features and maintenance contracts. What a healthcare facility needs to consider with the anticipated gains in productivity and patient throughput is whether there is adequate exam volume for a timely return on its investment (ROI). Facilities also need to consider the total cost of operation and ownership.

"Many of these devices are costly and, if they break, are fairly costly to fix, too," says J. Anthony Seibert, PhD, professor of radiology (physics) at the University of California, Davis. "There are a lot of intangibles many people ignore or do not appropriately indicate in terms of total cost of ownership and maintenance, when they try to do a cost justification of DR."

DQE - detector quantum efficiency

Image quality depends on spatial resolution, contrast resolution and detection efficiency - or how efficient the dose or incident radiation is in creating the final image.

DQE is a measure of detector efficiency and signal-to-noise performance. DQE is one indication of a system's efficiency in utilizing the input signal-to-noise ratio and how that will be converted into the output single-to-noise ratio in the image, respective to the incident dose. But, even a high DQE number is not a guarantee of a perfect DR system.

DQE "needs to be measured both as a function of exposure level and as a function of spatial frequency," says Rich VanMetter, PhD, physicist and clinical studies manager for Eastman Kodak Co.'s Health Imaging Group. "It would be nice if it were just a number, but it is a complex, multi-dimensional function. Invariably, one function is higher in one place and another function is higher in another place and you're left scratching your head wondering which one is better."

Image processing

Every major vendor has its own independently developed image processing technology to segment and analyze image data to produce a tonal rendering of the image. Bad pixel correction is an important part of imaging processing. A detector could have a high DQE number, but if the system does not display well, the reader will not extract the information from the image.

Any DR system "is only as good as the weakest link," says UC-Davis' Seibert. "You can have the perfect system, but if you don't image process or you don't manipulate the image correctly after it has been acquired, the images will look unacceptable to a radiologist."

"The unfortunate thing about image processing is that it is very difficult to compare vendor A and vendor B," says VanMetter. "Image processing is a suite of capabilities. Every vendor's image processing has parameters that need to be set for the needs of a specific institution."

Ease of use/training

When Carolinas Medical Center installed its DR units, Radiology Chief Christopher G. Ullrich, M.D., said the facility underestimated how long it would take some of its analog technologists to make the switch to DR, "because they had been so used to shooting dark films. When we went to DR, the overexposed film no longer was judged to be that of good quality."

In some cases, technologists also may need to learn different patient positioning techniques when using a digital C-arm, conventional table design or wall stand.

"There is no excuse for turning in a film that wasn't positioned well in a DR system, because you can see it and make the correction almost immediately," adds Ullrich. "You can make on-the-fly corrections in DR with much more flexibility."

Bottom line

Which DR technology performs best is fodder for debate. In studies that compare direct and indirect flat-panel technologies, a clear-cut difference in image quality has yet to emerge.

Integrating the RIS for workflow management also is extremely important - a DR system that does not integrate well with the RIS could force a radiologist or physicians to work from multiple review stations.

"Very deep project planning," recommends David Channin, MD, associate professor of radiology and chief of imaging informatics at Northwestern University Medical School and chief of PACS at Northwestern Memorial Hospital in Chicago. "The devil is in the details. You can't do this from 20,000 feet up; you have to get down there in the mud."

Proper planning can facilitate the correct choice of PACS technology, affordable short-term and long-term storage options, efficient radiology department workflow configurations, and adequate training and staffing. Most of all, teamwork is most critical.

Close cooperation between IT and radiology is essential, says John Warner, MD, assistant chair of the radiology department at the Marshfield (Wis.) Clinic and chair of the PACS committee. "We have had radiology working hand-in-hand with IT from the first conceptual meeting seven years ago. I am a strong believer that unless you have IT 100 percent completely involved, your chances for success are certainly diminished."


Marshfield Clinic Center is the hub to one of the largest rural clinic systems in the United States, with more than 700 physicians in 41 regional healthcare centers throughout Wisconsin. Marshfield Clinic Center installed its PACS three-and-a-half years ago and continues to expand it today to affiliated facilities. Total volume throughout the network is approximately 600,000 studies annually. Marshfield also shares some 3.5 million patient files in a combined electronic medical record (EMR) with St. Joseph's Hospital, a 400-bed level II trauma center on the Marshfield campus. The campus went filmless early this year.

Marshfield faced several challenges, including the distribution of images, both at its main campus and throughout its geographic network.

Marshfield Clinic Center initially installed a dedicated 100-megabyte (MB) switched network to support PACS image movement. Once the center's house network configuration was upgraded to 100-MB switched, the need for a separate image network was eliminated. Image data now share the same network with all other traffic.

Marshfield also is using high-speed fiber connections between sites that allow for sufficient bandwidth - 35 MB or 50 MB - to move images and data across the same network with minimal - if any - noticeable delay.

"It's a challenge for us, because we are in a rural area," says Lane Solverud, Marshfield Clinic's RIS manager. "In a city or a more urban area, a variety of high-speed communication options are available at reasonable prices. It isn't that way in central and northern Wisconsin."

Marshfield Clinic Center also depends on some 170 strategically located clinical review workstations throughout its facilities for image access. Deployment is based on how many exams a physician requests, department use for treatment planning and department size, including the number of physicians and physical layout of the department.

Within the hospital, image review station deployment is based on providing image review in close proximity to the point of patient care. For example, there is a review station in every ER and trauma room, so the surgeon does not have to leave the patient to review diagnostic studies. Every ICU has at least one and sometimes more than one review station, while all clinical floors have at least one and generally more. Each operating room also contains a dedicated image review station.


A facility's success in managing digital x-rays also depends on its financial and human resources.

"A PACS is a long term IT infrastructure investment that will have a much longer lifespan [than an imaging modality], and you have to budget for that as it will need to evolve as the institution evolves and grows," says Northwestern's Channin.

For the University of Pennsylvania Health System (UPHS), the choice was made to reinvest its total annual film budget of $5 million in digital technology and a PACS. Yearly expenses for the four-hospital system in the greater Philadelphia area included purchase of the film itself ($2.2 million to $2.3 million annually), as well as file storage, a film library, staff, chemicals, disposal and other ancillaries. UPHS facilities perform approximately 700,000 exams per year.

The transition from film to digital has been completed at two facilities. The third hospital went live with its radiology information system (RIS) around the first of the year, while the PACS installation should be completed by March. The fourth hospital is scheduled to have its RIS and PACS in place by the end of this year. By mid-year, approximately 80 percent of the system will be fully integrated with the RIS-PACS.

"Not everyone can spend $5 million a year," concedes Alberto Goldszal, PhD, director of medical informatics in UPHS' radiology department. "If you have critical mass and put together hospitals to come up with that kind of money, then you can convert it financially into a good deal."

UPHS figured its break-even point was 400,000 exams per year to justify the conversion to a filmless environment.

Memorial Hospital in Colorado Springs, Colo., made its choice to go digital - initially with computed radiography (CR) - rather than replace its film processors with the next generation of the technology. Also influencing the digital decision was the planned construction of Printer's Park Medical Plaza.

The campus includes a 475-bed hospital, Printer's Park Medical Plaza outpatient facility with full-service radiology department, a breast care center and an independent orthopedic group. Memorial Hospital and Printer's Park are completely digital except for film-based mammography and some invasive applications. The facilities handle approximately 700 exams per day.

"It didn't make sense to invest all that money in a new facility with old technology," recalls PACS Administrator Tony Shaner.

One ongoing challenge is staying on top of software upgrades for both the PACS and digital x-rays equipment and maintaining image quality.

"Upgrades on the DR room may affect how images look on the PACS. We are constantly working with the modality vendors to keep the image quality optimal," Shaner adds. "I haven't had an instance where an upgrade on the PACS has affected image quality, but certainly it may happen when the vendor upgrades the DR system software."

Among Memorial Hospital and Printer's Park benefits have been enhanced productivity and throughput. Shaner cites the decline in "image availability time" from 36 minutes to seven minutes from the time a patient arrives in radiology until the images are available in the ER. Now, it takes longer to change patients than it does to take the images. The private orthopedic practice has two DR rooms and can take as many as 150 exams (total for both rooms) in an eight-hour period.


Healthcare providers also need access to patient images quickly. To gain that swift access, facilities must determine how long images stay in short-term storage for near-immediate access.

Northwestern Memorial Hospital has some 720 beds and performs approximately 350,000 radiology procedures per year, 95 percent of which have been filmless since March 1999. With some 1.5 million studies in its PACS and approximately 70 million images, Northwestern has a total of 15 terabytes of (lossless) compressed storage capacity on-site and off-site.

To have expedient access to a patient's digital x-rays, Northwestern determined its on-site storage requirements for fast access by calculating how many months of storage the facility needed to meet a certain percentage of user-viewing demands. Northwestern concluded it needed about 1 terabyte per month for short-term storage.

"Given our case mix, we need roughly 120 to 160 days of fast storage - which means we can display any image in that fast storage in five to 10 seconds to meet better than 90 percent of viewing episodes," says Channin. So, Northwestern chose 4 terabytes for four months worth of on-site storage, and may increase that amount to 6 or 8 terabytes as soon as the third quarter of this year.

Image volume is growing by approximately 10 percent per year, due to an aging population, new uses for images, and new technologies. In addition, the size - or number of slices - of CT and MR studies is growing.

Printer's Park needs less storage capacity, based on its volume. One terabyte can satisfy four months of immediately accessible digital images.

To gauge its needs, PACS Administrator Tony Shaner says the facility estimated the size of a digital chest x-ray image at 16 to 17 megabytes (MB) and computed radiography (CR) images at 11 MB each. MR and CT have image sizes of 0.5 MB each. At 10 images per exam, 10 CT exams with 100 images each would need 50 MB of storage space. (For a complete chart of image size by imaging modality, see page 40.)


Staffing and training also are key issues in managing digital x-rays. Marshfield Clinic has five PACS administrators on-site to provide 24/7/365 support for its PACS; all five have either an IT or radiology background.

Lack of technical support, like in many areas, can lead to problems. Healthcare providers depend on timely information for appropriate patient treatment. Medical imaging is an essential component of that information and must be available reliably and quickly. A significant cause of poor acceptance of PACS has been system support and training resources for users.

"I have seen major academic institutions have their multi-million-dollar PACS deployment fall apart for that very reason," says Warner. "They would hire a very limited number of PACS administrators with good IT backgrounds to support the system and it would fall apart."

Marshfield's Solverud says that Marshfield Clinic has recruited PACS administrators from both the IT and radiology areas of their organization. He says this blend of skills works well for the Clinic. IT skills come in handy for technical support of the PACS components, project management, and in working with vendors. Radiology skills are primary in day-to-day support of the technologists and radiologists, since this requires the ability to determine image quality and to understand how the images are collected and used.

At UPHS, Goldszal found that the staff had a more difficult time learning how to use the RIS, adding that it took "considerable re-engineering" to get everyone trained.

"The existing staff will need to deal with the RIS, not so much the PACS," he adds. "The RIS touches everyone's business in radiology, from getting the patient admitted to processing all the clinical information about the patient and then producing a report on the back end."

Having experience on the UPHS RIS made the PACS that much easier to learn.

"Most important is the person you have and the commitment he or she has," offers Shaner. "This will be something you eat, drink and sleep from that point forward."

Digital X-ray Checklist
  • Having the right people on both the radiology and IT side of any image management project is the first key to success and efficiency, says Patrick Milostan, chief technology officer (CTO) with IT consulting firm CareTech Solutions. CareTech Solutions, as part of an outsourcing agreement with the hospital, recently completed an installation of a PACS at North Oakland Medical Centers in Pontiac, Mich. The urban hospital has approximately 300 beds, with a patient volume that can be as high as 70,000 radiology studies per year. 
  • Second, a hospital must make sure its picture archiving and communications system (PACS) can be "easily maintained and backed up. Make sure there is redundancy, because, as you take off line the actual x-ray, you need to make sure there is redundancy in case there is any kind of technical snafu and the radiologist is able to get to the x-ray for comparative studies."
  • The correct PACS technology depends greatly on the size of facility, volume of images and the cost structure of the PACS itself.
  • "From a technology perspective, you have to make sure that the process flows through the hospital and off-site facilities," Milostan adds, "and how do you move that same image outside of the hospital in a secured environment to go to a radiologist's home?" 
  • One way is to make sure there is adequate line speed and bandwidth so digital x-ray images do not get bogged down with data from other imaging modalities or other departments within a hospital. "On an internal basis, you want to make sure [digital x-ray images] are on a separate VLAN (virtual local area network), so the PACS images are not transferred across the whole network and there is no interference with any normal traffic," Milostan says.
  • A switch can separate the images so they have their own separate space on the VLAN. Milostan says 100-megabyte (MB) speed should be the minimum standard internally.
  • From a WAN perspective, a facility should make sure it has enough bandwidth on its line to keep images moving smoothly and rapidly. Milostan recommends a "T1 line or better, because if you go with a smaller line - even with a Web browser - you don't want physicians to take five minutes to bring up an x-ray." 
  • As a rule of thumb for digital x-ray storage, Milostan says a facility should have enough storage to keep images readily available for up to six months. Depending on the volume of studies, one terabyte of storage may suffice. "However, make sure it is not just that terabyte, but there is the redundancy with the net terabyte. I am not recommending a facility go buy four-years worth of disks. You take the step you need to get through about a year's worth of data on-line real-time."
  • A strong uninterruptible power supply (UPS) also is a wise choice where the x-rays are stored and at the radiologists' workstations.
  • Also, design the radiology department to facilitate the flow of images. Locate review workstations that are easily accessible to a radiologist and his or her images.
  • "If you're putting in a PACS, it doesn't mean you just take your view boxes off the wall and put monitors there," Milostan says. "If you have a radiologist reading a particular type of exam, you don't want to bungle the process. It is different in every place. In some places, radiologists read all types of exams; at other places, radiologists read certain types [of exams]."