An imaging plate is used in computed radiography (CR) instead of a conventional film cassette.
The imaging plate is coated with photostimulable phosphors. The phosphor layer is doped with special substances to alter the crystalline structure and physical properties. After radiation, the enhanced phosphor material absorbs and stores x-ray energy in gaps of the crystal structure, building a latent image.
Usually, the storage phosphors are stimulated with a low-energy laser to release visible light at each point of x-ray absorption. To read-out the image, the plate is inserted into a computed radiography scanner. The scanning laser beam causes the electrons to relax to lower energy levels, emitting light that is captured by a photo-multiplier tube and converted into an electrical signal. The electronic signal is then converted to digital data and can be displayed on laser-printed films, workstations, transmitted to remote systems, and stored digitally.
The CR units automatically erase the image plate after the complete scan. Phosphor imaging plates, like film, are stored in cassette format and can be re-used very often if they are handled carefully. Existing conventional x-ray equipment, from generators to x-ray tubes and examination systems, can be used with imaging plates.

(CR) Computed radiography is an imaging technique that uses similar equipment to conventional radiography except that films are replaced by imaging plates. An imaging plate contains photostimulable storage phosphors, which store the radiation level received at each point in local electron energies. The imaging plate is placed under the patient in the same way as conventional film cassettes. After x-ray exposure, the imaging plate is run through a special scanner to read out the image. The digital image can then be processed to optimize contrast, brightness, and zoom. Computed Radiography can be seen as halfway between film-based conventional technology and current direct digital radiography.

An intensifying screen is used to intensify the x-ray effect during radiation exposure of the x-ray film. Approximately 5% of the x-ray photons will be absorbed by the film only. Intensifying screens consist of a sheet of inorganic salts that emits fluorescent light when stroked by x-rays. The fluorescent input and output screens of the image intensifier are very similar to intensifying screens.
Calcium tungstate and rare earths are two common salts (also called phosphors) used for intensifying screens. For example, a calcium tungstate (CaWo4) screen can absorb around 40% of the x-ray photons and convert the radiation into light photons. A basic feature of this screen types is related to the position of the k-edge on the energy axis. Tungsten (W) is a heavy element has a k-edge at 69.5 keV, while that for rare earth elements is in around 50 keV.
The fraction of x-rays absorbed by a screen is depending on the speed. Factors affecting the speed of a screen: Mammography cassettes contain usually one intensifying screen, but most others use two screens per film cassette. The intensifying screen as part of a film screen system has been an important component in radiology to reduce the radiation dose of the patient. Today, the conventional film cassette is being replaced by an imaging plate used in digital systems.

See also Actinides, Cinefluorography and Added Filtration.

The latent image is the invisible product of x-ray or photographic film emulsions, build after radiation or light exposure. The visible image is developed and fixed chemically from the latent image. Latent images are also produced in a photostimulable storage phosphor and retrieved by scanning with a laser.

See also Developer and Imaging Plate.

Xeromammography or xeroradiography is a breast imaging. Xeroradiography uses photoelectric records of x-ray images on a coated metal plate. Xeromammography as distinct from film-screen mammography uses low-energy photon beams, long exposure times and dry chemical developers.
Although xeromammography has sensitivity and specificity comparable with those of a film-screen mammogram, it is not recommended for screening or diagnostic mammography because of maintenance problems and the need for higher breast radiation doses compared with modern low dose mammography equipment.