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Computed Radiography (CR) uses very similar equipment to conventional radiography except that in place of a film to create the image, an imaging plate is used. Hence, instead of taking a film into a darkroom for developing in chemical trays, the imaging plate is run through a computer scanner to read and digitize the image. The image can then be viewed and enhanced using software that has functions very similar to conventional image-processing software, such as contrast, brightness, and zoom.
Differences from Direct Radiography
Computed radiography is commonly distinguished from Direct Radiography (DR). In the same way that a CR system requires a short burst of radiation, so does a DR system. The difference is that on exposure a DR system will almost instantly display the image on the screen in front of the radiographer, therefore removing any need for processing. Post production can of course be performed on DR images in the same way that CR images can.
This is NOT to be confused with Fluoroscopy, where there is a continuous beam of radiation, and the images appear on the screen like on a TV. This is the system most people are familiar with, as this is what is used in airport security systems.
The imaging plate contains photostimulable storage phosphors, which store the radiation level received at each point in local electron energies. When the plate is put through the scanner, a scanning laser beam causes the electrons to relax to lower energy levels, emitting light that is measured to compute the digital image. Imaging plates can be re-used thousands of times if they are handled carefully, although handling under industrial conditions may result in damage after a few hundred uses. An image can be erased by simply exposing the plate to a room-level fluorescent light, and the plate is then ready for re-use. In the software, the scanned image is encrypted so that the original data is kept secure and can not be tampered with.
Common applications for computed radiography include:
Radiographic testing using computed radiography has pros and cons:
Categories: Radiography | Nondestructive testing
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Computed_radiography". A list of authors is available in Wikipedia.|