Managing Digital X-rays

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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,