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Digital radiography drives CR and DR toward common ground


When digital radiography began to take hold, it seemed computed radiography -- the phosphor-based means to a digital end -- would be dropped by the wayside. Conventional wisdom held that it would be only a matter of time. But nothing like that has happened.

When digital radiography began to take hold, it seemed computed radiography - the phosphor-based means to a digital end - would be dropped by the wayside. Conventional wisdom held that it would be only a matter of time. But nothing like that has happened.

Radiology departments used CR to step up to digital x-ray, justifying the purchase of a phosphor plate reader as a stepping stone to the future. Then a funny thing happened. The departments started to like CR. And the CR companies, recognizing that DR has advantages, began to look for ways to make CR more like DR.

Agfa's "DR equivalent" is the DX-S, which combines a DirectriX needle phosphor imaging plate with Scanhead line-to-line CR simulation and light collection technology to improve image quality and accelerate imaging time. The needle imaging plate converts energy from x-ray to light two and a half times better than standard CR plates do, making the detective quantum efficiency (DQE) that much better, according to the company. Scanhead, which can run 120 to 140 plates an hour, increases throughput, decreases waiting time for cassettes, and provides rapid access to digital images.

The cesium bromide crystal-based Focused Phosphor technology from Fujifilm Medical Systems USA is being touted by company executives as a competitive alternative to amorphous selenium or silicon technology. By using a pixel layer of phosphor, Focused Phosphor improves digital quantum efficiency twofold, said Penny Maier, national marketing manager for Fuji Digital X-ray.

In conjunction with HD LineScan, which reads plates line by line rather than point by point, Focused Phosphor brings Fuji products up to DR speed, according to Maier. Images start appearing in two seconds and are finished in seven. The entire image cycles in 10 seconds.

Konica Minolta has developed its own cesium bromide columnar fiber crystal structure for the new Regius 370 upright CR. Regius also has a built-in antiscatter lead sheet to reduce x-ray scattering and improve image sharpness, two scanning resolutions, 87.5 micron and 175 micron, and a hybrid processing algorithm to remove image artifacts and enhance clarity.

Agfa, Fuji, and Konica Minolta are wedging their products into a market niche that wants DR but will take CR if offered the right inducements. At stake is nothing less than the future of CR.

Industry pundits believe that about 90% of large teaching institutions have converted to digital, and the percentage of digital 300 to 400-bed hospitals doing so approaches 75% or 80%.

"The radiology market in large university hospitals is saturated with PACS and CR," said Ralph Schaetzing, Ph.D., technical director of digital imaging at Agfa Healthcare. "They're now in the replacement business and looking for a digital solution, digital workflow, to get efficiency up."

Bringing out "DR equivalents" is a response that could serve these CR vendors well in other markets. Digital x-ray is just beginning to move into community hospitals and large multispecialty clinics, traditionally cost-sensitive marketplaces seemingly made to order for CR.

But DR manufacturers are not standing still.

While CR vendors beef up their technology to rivalDR in image quality and productivity, DR suppliers are developing smaller, more compact products to challenge CR in affordability and flexibility.

"Ultimately, the justification for DR and CR, for digital radiography in general, will always be an economic one. So we have to have the right answer within an economic scenario," said Arne Helbig, international marketing manager, general x-ray systems, for Philips Medical Systems.

Comfortable, for the most part, with the image quality produced by their flat-panel digital detectors, DR venders are responding to the spread of digital technology to small institutions by becoming sensitive to cost. Philips' DigitalDiagnost Compact Solution, shown for the first time at the 2005 RSNA meeting, is a step in that direction, according to the company.

Designed to cover all general radiography applications at a moderate throughput rate, DigitalDiagnost Compact has a 17 x 17-inch flat detector that is mounted on a fixed multipurpose stand equipped with a tilting and swiveling arm, a trolley with a four-way floating tabletop, and a ceiling-suspended tube carrier.

The Definium AMX 700 from GE Healthcare is another example, bringing GE's amorphous silicon flat detector to virtually any portable imaging situation, according to the company. The unit, introduced at the RSNA meeting, has a large, 16 x 16-inch field-of-view, touchscreen digital display, large casters and wheels, pressure-sensitive power steering, and variable speeds up to 3 miles an hour, and a 0.75-mm focal spot.

Similarly, the work-in-progress DirectView DR 3000 system from Eastman Kodak was designed to meet the needs of midsized hospitals, outpatient imaging centers, and orthopedic practices. It has a motorized floor-mounted U-arm that can used for general radiology exams - including those requiring cross-table positioning - a movable table, and a 17 x 17-inch imaging area.

Adding more fuel to the flat-panel fire is the ddR Formula system from SwissRay International, which can be configured with either a solid-state detector or the company's conventional CCD-based detector. The FP-5000 amorphous silicon detector with a cesium iodide scintillator, which is being supplied by Thales, has a spatial resolution of 3.5 line pair/mm and 143-micron pixel detail detection capability. The C-arm centers the x-ray tube to the detector for precise and convenient patient positioning. It also offers ddART, a backlit design with a variety of pieces of artwork, including cartoon characters and sports themes, on its front cover to improve the ambience of the imaging room.

As manufacturers vie for position in the digital imaging marketplace, they are loath to give competitors an edge. In their battle for customers, like Republicans becoming environmentally aware and Democrats reaching out to big business, DR and CR vendors are finding more and more in common.

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Nina Kottler, MD, MS
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