reusable fim)

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. The imaging plate is placed under the object to be examined and the x-ray exposure is made. Hence, instead of taking an exposed film into a darkroom for developing in chemical tanks or an automatic film processor, the imaging plate is run through a special laser scanner to read and digitize the image. The digital image can then be viewed and enhanced using software that has functions very similar to other conventional digital image-processing software, such as contrast, brightness, filtration and zoom.

Differences from Digital Radiography

Computed radiography is commonly distinguished from Digital Radiography (DR). The difference is that after exposure a DR system will almost instantly display the image on the display in front of the radiographer, therefore removing any need for processing. Image processing or enhancement can of course be performed on DR images in the same way that CR images can due to the digital format of each. There are many different types of DR detectors in use in medicine and industry. Each type has its own merits and distinctions and may be applied to certain imaging requirements based on these attributes.

Imaging plate

The CR 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, the scanning laser beam causes the electrons to relax to lower energy levels, emitting light that is detected by a photo-multiplier tube, which is then converted to an electronic signal. The electronic signal is then converted to discrete (digital) values and placed into the image processor pixel map. Imaging plates can theoretically 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. Most laser scanners automatically erase the image plate after laser scanning is complete. The imaging plate can then be re-used. In the software, the scanned image is encrypted so that the original data is kept secure and can not be tampered with. Reusable phosphor plates are environmentally safe.

Industrial applications

corrosion surveys on pipes, often through insulation;
Examination of valves for erosion;
Information shots on industrial components; e.g. checking to see if a valve is closed properly, or checking for obstructions in valves and pipes;
Examination of boiler water walls;
Weld examination for certain ASME code applications
Automotive casting inspection
High pressure braze joint inspection (aerospace)
Wax pattern core integrity verification in investment casting foundries

Advantages

No silver based film or chemicals; instead a computer is used.
Exposure times are a fraction of typical film exposures, which reduces occupational exposure to radiographers in field applications and is more economical.
Image acquisition is much faster; commonly one minute instead of seven minutes, as with conventional radiography.
By adjusting image brightness and/or contrast, a wide range of thicknesses may be examined in one exposure, unlike conventional film based radiography, which may require a different exposure or multiple film speeds in one exposure to cover wide thickness range in a component. Computed radiography often requires fewer re-shots due to under- or over-exposure.
Images can be enhanced digitally to aid in interpretation.
Images can be stored on disk or transmitted for off-site review.
Ever growing technology makes the CR more affordable than ever today. With Chemicals, dark room storage and staff to organize them, you could own a CR for the same monthly cost while being environmentally conscious, depending upon the size of the Radiographic Operation.