What type of image receptor is calcium tungstate used for?
For decades, x-ray screens have been made of calcium tungstate because it emits light in the violet to blue spectrum, a color of light that is readily absorbed by x-ray film.
Why are intensifying screens used in radiography?
Intensifying screens are used in the x-ray cassette to intensify the effect of the x-ray photon by producing a larger number of light photons. It decreases the mAs required to produce a particular density and hence decreases the patient dose significantly.
What are the materials used as intensifying screens?
An intensifying screen is a plastic sheet coated with fluorescent material called phosphors. Phosphors are materials which convert photon energy to light. LUMINESCENCE is the emission of light from a substance bombarded by radiation.
What is calcium tungstate screens?
The 200 Speed Blue Emitting Calcium Tungstate Screen is the most commonly used Non-Rare Earth intensifying screen. With a faster speed than Detail or Medium speed screens, the Hi-Plus Intensifying Screen provides an efficient balance between the time patients are exposed during x-rays and image quality and detail.
What is intensifying screen in radiology?
Who developed calcium tungstate in screen?
Edison
By March of 1896, Edison had incorporated this material into a device he called the Vitascope (later called a fluoroscope), that consisted of a tapered box with a calcium tungstate screen and a viewing port.
Which is faster, rare earth intensifying screen or calcium tungstate film?
Incorrect matching of the film and screen will result in a slower film/screen system speed, which means using a longer exposure technique. Rare-earth intensifying screens are faster than calcium tungstate film/screen systems and do not sacrifice resolution. They have, therefore, widely replaced calcium tungstate systems.
What kind of screen is used to intensify radiation?
Calcium tungstate and rare earths are two common salts (also called phosphors) used for intensifying screen s. For example, a calcium tungstate (CaWo4) screen can absorb around 40% of the x-ray photons and convert the radiation into light photons.
Why are cassettes used for intensifying screens?
Cassettes are used in association with intensifying screens and screen films. They have related functions: 1. to contain a film 2. to exclude light, 3. to maintain the film in close, uniform contact with both screens during the exposure 4. to protect the intensifying screens from physical damage.
What is the intensity factor of a screen?
The intensity factor is a measure of efficiency of intensifying screen, and is the ratio photon exposures with and without intensifying screen to achieve a designated film density. The absorption and conversion efficiency of the screen affect the intensity factor.