Digital Radiography Adds an Extra Dose of Efficiency

hiit040505.jpgConsider it akin to dramatic alignment of the stars propelling adoption of digital radiography systems. It was only a matter of time until this technology began grabbing a toehold in radiology departments, once CT, MR and PET systems were installed, and institutions obtained the necessary image management capabilities of PACS.

With general radiography lagging behind in the analog world, true efficiency was illusive. In the beginning, many institutions turned to computed radiography because of the ease of a retrofit into their existing x-ray systems, and the cost of CR was easier to justify. However, as DR technology evolved — with increased speed of image acquisition leading to improvements in throughput and better image quality — many hospitals and imaging centers have considered DR systems as an answer to their digital imaging needs in general radiology, orthopedics and trauma centers. For the most part, DR is a replacement technology for analog rooms as well as new x-ray rooms. CR, in contrast, tends be installed based on the need to retrofit an existing department to digital and meet new workflow needs.

Industry analysts from Frost & Sullivan released a report in January that suggests digital x-ray systems adoption has been increasing since 2002. Overall, the marketplace estimates the DR growth rate at about 5 percent annually. As these systems improve their capabilities and cost considerations decline, Frost & Sullivan deems the digital x-ray market to be vibrant with opportunities for growth robust. Currently CR outsells DR at a ratio of 10:1 with a reported 602 DR units sold in 2005 as compared to 5,000 CR units during the same time frame. Industry estimates place CR growth in North America between 15 and 30 percent annually, which has slowed from prior years largely due to market saturation, which is estimated at about 50 percent.

Although CR units are significantly less expensive than DR — the average DR system ranges from $400,000 to $500,000 range, while CR systems typically sell for $200,000 to $300,000 — there are drawbacks in the speed of image display due to the necessary steps in accomplishing CR studies. With DR, the image is captured and displayed within seconds on a workstation.

Currently, many radiology departments in hospitals and free-standing imaging centers must contend with a combination of DR, CR and analog systems. Once these facilities are able to fully integrate digital imaging across all modalities, they anticipate increased efficiency will be enabled.

J. Anthony Seibert, PhD, professor of radiology at the University of California at Davis anticipates a paradigm shift away from CR towards DR.  With two types of detectors, direct and indirect, and pros and cons to each type, he explains that the new charged coupled device (CCD) detectors have made inroads towards adoption of DR technology.

"If you asked physicists five years ago about the possibility of having a useful CCD detector in diagnostic radiology, they would have said it couldn't happen because of a phenomenon called a secondary quantum sync that occurs at a point in the cascading of the signal from the acquisition of the X-ray through various processing steps," he explains. Technologic breakthroughs, including the use of Cesium iodide as a structured phosphor as opposed to a non-structured screen produces better light capture efficiency, and thereby secondary quantum sync does not occur. Additionally, improvements in the lens systems have been developed.  "Those two phenomena coupled together have made the CCD camera-based DR system fairly functional and dose efficient."

In describing the Imaging Dynamics Corporation Xplorer DR system in particular, Seibert notes that a 16 million pixel CCD camera (4096 X 4096 pixels) reflects back to a large area simulator resulting in a spatial resolution sampling of about 100 microns. "So for a large field of view DR system, it has high sampling."

Meanwhile, in the world of DR, systems offer increased image resolution with reduced radiation dose, and attractive price points.  Innovative enhancements such as automated functionality have improved efficiency and throughput while adding to the ease of use for technologists. Such advances have increased the attractiveness of DR for sure.

Automated functionality = improved efficiency

Don Schreiner, BA, MBA, chief operating officer for Rockford Orthopedic Associates in Illinois, describes their evolution from one Swissray Modulaire system to their purchase of two ddR Formula and one ddRCombi Trauma for their fully digital orthopedic clinic due to open in July. Their experience with the first system, that improved throughput dramatically as well as garnering enthusiastic support from their technologists led them to make the decision to increase the number of Swissray systems in the new setting.

This 15-physician practice includes orthopedic surgeons, rheumatologists, podiatrists and physiatrists and expects to "go live" with an electronic medical record (EMR) system by the end of this year. They accomplish 300 to 400 imaging exams per day now, and anticipate a higher volume of studies as they add three more physicians this year. Their studies fall into the musculoskeletal family including routine orthopedic exams, bone densitometry (DEXA) and electromyographs (EMGs). They have a surgical center on site for performing outpatient procedures.

"Throughput has improved because everything is automatic, so there is little moving the equipment manually," Shreiner explains. Swissray's Automated Positioning System (APS) is designed to streamline radiology workflow by automating all steps relating to patient positioning and image acquisition. Patient data can be transferred directly from the RIS/HIS via DICOM worklists, with exposure and image processing parameters selected using a simple touch-screen. Swissray's robotics position the system for a given examination by remote control, while an integrated video camera monitors the patient to ensure correct positioning. Once the image is captured, all data are stored under a DICOM header.

An off-site facility that provides orthopedic services for Strong Memorial Hospital in Rochester, N.Y., installed a Kodak DirectView 7500 System in November 2005 as a beta trial site. The 33 orthopedic physicians in this ambulatory care center see 700 patients who require between 250 and 300 x-ray exams per day.

Cindy Redmond, RT(R) radiology manager in this center, describes the system as very efficient with the ability to accomplish 25 to 30 percent more work in that room as compared to their CR systems. "We may do 35 to 40 patients in the DR room compared to 19 to 20 in another [CR] room." The images appear on the screen approximately 7 to 10 seconds after exposure, as compared to the CR units which require a minute or so to complete view an image. Additionally, she notes that they rarely have to repeat exams, using a preset exposure index range from 1500 to 1700.

Redmond appreciates the auto-centering, auto-positioning and tracking functions of the system. "With auto-centering, you can place the patient on the table, your [x-ray generating] tube can be sitting somewhere else in the room. When you hit the auto-centering button, the tube automatically floats over to the table and centers itself to the detector. If you get the patient's anatomy positioned correctly over the detector, the tube will find it."  Following their positive experience with this system, they have installed two Kodak DirectView 7500s in the trauma center at Strong Memorial.

The DR system uses modular components that can be configured to fit into an institution's space, procedures, workflow and budget. There are single- and dual-detector options to perform a variety of general radiography examinations including trauma. There are additional software options available, and the system is capable of obtaining patient data directly from the facility's HIS/RIS to eliminate the need for manual data entry with optional Kodak DICOM work list management service user software.

David Fisher, MD, an orthopedic surgeon at the TRIA Orthopaedic Center in Minneapolis, estimates that they image close to 250 orthopedic and sports medicine patients per day. This completely digital, state-of-the-science orthopedic center includes a surgical center, general and sub-specialty clinics, rehabilitation services as well as an education and research center. They installed a GE Healthcare Definium 8000 DR system in October 2005. They have found the speed of the system to be quite beneficial, and the quality of the images they obtain is exceptional.

"We can measure angles and distances using the images for doing measurements," he explains. Besides the obvious workflow improvements, he also notes that patients seem to appreciate the immediate digital presentation of their images on the screen for educating them on their condition.

The facility is making good use of the system's Auto Image Paste capability. This element provides physicians with a single view of anatomic structures, particularly the spine and legs, without any visible seam lines. Prior to this, technologists complained that it took a long time to manually paste multiple images together, which physicians need to provide a level of accuracy for their work. "Our physicians can now image even the tallest patient," says Fisher.

Quality issues require careful consideration

Cindy DuPree-Thompson, ARRT, CRT, chief technologist at the University of California at Davis Health System installed three IDC Xplorer direct capture DR systems in outpatient settings with two of those systems used in primary-care clinics that are located several miles from their campus. She notes that it does take time to "tweak" image quality and that their radiologists worked with IDC application personnel to optimize image quality. "The end image quality for any digital image is dependent on the technique used and manipulation of the image by the software is critical. You must work closely with the application people to optimize image quality." Their musculoskeletal physicians are quite pleased with the image quality.

Besides image quality issues, DuPree-Thompson appreciates the 17x17-inch field-of-view detector because it often means they are not required to take two PA chest views to cover the entire lung field on large or tall patient. "For an outpatient environment, this system is fine. DR in general improves speed because you don't have to handle cassettes, and we see the image within 5 to 20 seconds, so it increases throughput."

Further, they appreciate the ease of use of their DR systems. Many of their technologists are older adults, some are pursuing a second career and enter the field in their 30s and 40s. While a radiology tech job can be quite physically demanding, she says that DR goes a long way towards making it easier. They have interfaced their DR with their RIS and PACS.

IDC has worked to not only improve image resolution with 4.6 lp/mm, but to price their systems competitively, within the range of CR systems — with a list price in the low $100,000s if they are able to use the institution's current x-ray system. The detector is not "tiled" but is manufactured in a single 17x17 piece, so there are no seams which may require interpolation to provide missing data.

Improved throughput

When a healthcare facility switches from CR or analog to DR, they often note workflow improvements. Edward Blocker, MD, an orthopedic surgeon at Low County Medical Group in Buford, S.C., describes just that experience for their 15-man multi-specialty group that includes physicians in orthopedics, cardiology, oncology, gynecology and nephrology, among others. They installed the portable Canon CXDI-50G 17X17 sensor mounted into a C-arm by Quantum Medical Imaging.

Describing the image quality they obtain as vastly superior, Blocker explains that when they opened their office, they installed two CR units.  Once their imaging volume increased to the point where they were considering an additional CR system plus supplementation of their technical staff and increases in the number of processors, they reviewed the benefits of DR. "When we looked at the efficiency of the DR, we upgraded one CR room to a DR room, and now we only use one DR and one CR." Although they had an increased imaging load, they were able to decrease from a projected three rooms to only one room plus a fraction of another (the CR room).

Besides the obvious improved efficiency and enhanced image quality, Blocker says that their techs have become champions with this DR system and prefer to use it over their CR room.

Often the increased efficiency and throughput of DR systems yield significant economic benefits. Timothy Scalise, MHR, RT(NM), the imaging technical manager at McKay-Dee Hospital in the Intermountain Health Care System in Ogden, Utah, describes their practice in a 275-bed hospital. Throughout their radiology practice, they annually accomplish a total of 15,000 to 20,000 exams across all imaging modalities with about 4,000 to 5,000 in general radiology. Their department is completely digital with the exception of mammography. They have a total of six DR rooms, with four Siemens Aristos MX systems, one Aristos VX and another that is a TX model which is a floor-mounted tube that they needed to install due to engineering issues.

When asked about throughput advantages, Scalise says, "I would say it takes about one third of the time to complete the exams and we have not had to increase staff for the past three and a half years, even though the number of exams has increased by 25 to 30 percent."

Even though there is a learning curve involved in reading digital images, and he considers that there may be a slight reduction in detail in digital imaging, the radiologists have realized that there are other benefits to digital images because they can now change the contrast, or magnify images to gain new information. He stresses there is not a significant reduction in detail. "There are so many advantages to digital, like speed, where they can get the image within 30 seconds after it is acquired."

The Aristos FX Plus system, launched at RSNA 2005, is designed to be customizable and capable of integration into pediatric, trauma and orthopedic environments. In addition to the traditional adult design, the tabletop and supports are available in a pediatric configuration with child-friendly decals to reduce anxiety for the youngest patients.

This center did hire a PACS administrator from among their ranks of radiology technologists. Scalise says they have found that approach has worked best because the tech understands anatomy and x-ray information as a basis for performing their IT functions, with a bit of additional training. By using this staffing arrangement, they have developed a "home grown" quality assurance (QA) system with a "drop down window" where radiologists can make notes to help technologists learn from possible errors, such as if the image was a bit dark, or anatomy was cut off.  This function enhances communication between the radiologists and technologists and allows them to recall patients more quickly if necessary. It provides immediate feedback for techs and he believes their quality has improved as a result.

Decreased x-ray dose

One of the primary benefits DR affords is the reduced radiation dose to obtain high-quality images.

Hans-Peter Busch, MD, PhD, chief of radiology and medical director at the Barmherzige Bruder Hospital in Trier, Germany, has been using the Philips Medical Systems Digital Diagnost VM with one movable head in their emergency department. This system has two fixed, flat-detectors, one on the bucky table and one on a rail. This capability enables them to perform chest images from two angles. This university hospital with 600 beds accomplishes approximately 100,000 patient studies per year for their 30,000 inpatient days.

"We find that we can use half or less dose, in comparative studies comparing storage phosphor," Busch relates. "We can lower the dose by at least 50 percent." The flat-detector technology of this system is a Cesium iodide scintillator, amorphous silicon with nine million pixel matrix for the active square detector area of 17x17 inches with a Detective Quantum Efficiency (DQE) of up to 60 percent.

Busch describes using appropriate dosages depending on the type of exam to be accomplished. For example, when a patient has had a broken bone set with a metal plate and an x-ray is required to determine whether all portions of the plate system were surgically removed, the lowest level of radiation dose can be used for this purpose. "With a flat-detector, you can manage these parameters better."

In addition to specific dose benefits, this facility was able to reduce the number of exam rooms from three with film screen to two with digital because the DR systems are more efficient. Of course, Busch suggests that for high throughput, the institution must develop good systems for preparing patients and moving them in and out of the exam space. The most suitable patients for these exams are those who are mobile and those younger patients where half the dose is a benefit.

"The flat-detector system is like a 64-slice CT system — you must arrange the process around it and adapt processes for the best management of the unit." This system's workflow allows for full integration with a RIS and PACS.


DR systems have undergone remarkable advances in technology that enable them to answer myriad needs of busy imaging departments. The increased efficiency in rapid image production, automated procedures that facilitate better technologist and thus radiologist workflow, and reduced radiation dosages to benefit patients are some of the advantages to adoption of this technology.  As healthcare facilities upgrade from analog or CR to DR systems, they anticipate increased efficiency that will ultimately result in positive cost-benefit ratios in this era of containment of healthcare costs.