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Computed Radiography (CR) in Radiology Applications

11 July, 2011 | Computed Radiography

What is Computed radiography (CR)?

Computed radiography (CR) is a cost-effective solution to move from analog to digital imaging. With computed radiography (CR) the transition to digital is completed by installing computed radiography (CR) readers and replacing X-ray cassettes (which use X-ray film) with computed radiography (CR) cassettes (which use imaging plates). The imaging plates are exposed and inserted into the computed radiography (CR) reader. The computed radiography (CR) reader scans the plates, digitally displays the image on the workstation, and erases the imaging plate for reuse.

Computed radiography (CR) is a mature technology, which was developed in the middle of the twentieth century. It is currently in use in medical centers around the world. In many cases, it has replaced the process of taking X-rays on film in order to produce digital images. With these, better quality scans are possible, in shorter times, and with wider availability for study. The technology is found not only in medicine and dentistry, but in other areas, such as manufacturing for safety testing and analysis.

Traditional radiography, in use since its invention by W.C. Roentgen, in 1885, stores images on a photographic plate. Computed radiography (CR) can use existing X-ray equipment to take pictures but stores the images on a plate with phosphors that are activated and retained when the image is taken. A laser is used to scan the plate, which is converted to digital format. The results are then fed directly into a computer for interpretation. This simplifies the whole process, since no photographic development process is involved, meaning no dark rooms are necessary.

Since the early 1990s, it has become technically possible and economically feasible for digital imaging technologies to challenge film for projection radiography. This was made possible by certain prerequisite technological advances, such as high-luminance and high-resolution display monitors, combined with high-performance computer workstations which, though still costly, are now readily available. Electronic image archives that can efficiently store and retrieve the massive amounts of image data generated by projection radiography are becoming increasing cost- effective.

High-speed electronic networks with bandwidth adequate to transmit image files wherever and whenever needed are now accepted as an essential infrastructure component in health care.

Until the past few years, storage phosphor-based computed radiography (CR) has been the best alternative for acquiring digital projection radiography images. Computed radiography (CR) has the advantage of being fully compatible with existing x-ray equipment designed for film screen imaging. However, computed radiography (CR) has the disadvantage of requiring readout and processing steps that take about the same time as conventional film to obtain a diagnostically different has entered the medical imaging market, offering a new standard for digital x-ray image capture: digital radiography flat panel, solid state detectors with integrated, thin film transistor readout mechanisms.

Computed radiography (CR) and digital radiography (DR) have many similarities. Both computed radiography (CR) and digital radiography (DR) use a medium to capture x-ray energy and both produce a digital image that can be enhanced for soft copy diagnosis or further review. Both computed radiography (CR) and digital radiography (DR) can also present an image within seconds of exposure. Computed radiography (CR) generally involves the use of a cassette that houses the imaging plate, similar to traditional film screen systems, to record the image; while digital radiography (DR) typically captures the image directly onto a flat panel detector without the use of a cassette. Image processing or enhancement can be applied on digital radiography (DR) images as well as computed radiography (CR) images due to the digital format of each.

Advantages and Disadvantages of Computed Radiography (CR)

Computed radiography (CR) has its unique advantages:

  • Cost-effective solution for upgrading old X-ray equipment.
  • No silver-based film or chemicals are required to process films.
  • Reduced film storage costs, as the images are stored digitally.
  • Image brightness and contrast can be adjusted after the exposure.
  • Image can be processed and enhanced at any time after the exposure.

However, computed radiography (CR) has also some distinct disadvantages:

  • Manual handling of the cassette housing.
  • Imaging plates are expensive and can be easily damaged.
  • Inherent geometric lack of sharpness results in lower spatial resolution, as compared to film images.
  • Low signal-to-noise ratio and sensitivity to scattered radiation.

Moving to Digital with Computed Radiography (CR)

Changing healthcare needs require tomorrow’s diagnostic imaging service provider to rapidly produce the highest quality images, transmit them broadly, display them in alternative ways, and computed radiography (CR) image systems are an important element in this all-digital vision.

With digital image systems, the image data sent to workstations, printers, and archives is always identical to the original.

With improved workflow and increased efficiency, the all-digital radiology department will help hospitals, imaging centers, private practices, and clinics realize the full benefits of a picture archiving and communication system (PACS).

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