RADD 2501 Film Screen Systems - Overview

RADD 2501 Film Screen Systems - Overview - Film-Screen...

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Film-Screen Systems It is the visible light from the intensifying screen that actually produces the image on the film. Radiographic film is more sensitive to the wavelength of visible light than it is to that of x-ray. The use of intensifying screens reduces the amount of x-rays (mAs) necessary to produce the image. The film responds to the green-yellow wavelength light (rare earth) or blue-violet wavelength light (calcium tungstate) from the intensifying screens crystals. The film and the screen combine to have a given “speed” (think of photographic film). Speeds are relative to “100” or “par”. As system speed increases: patient exposure (mAs) decreases. One can purchase film-screen systems up to 1200 speed. Example: A 400 speed system would only require ¼ of the quantity of x-rays (mAs) to produce a given density compared to a 100 speed system. Compared to a 200 speed system, a 400 speed system would decrease the dose by half (1/2 the mAs). A 400 speed system is the lowest film-screen system that should be used for spine radiography. Knowing this, why doesn’t everyone go out and buy 1200 speed film-screen systems? As usual there are trade offs. You never get something for nothing:
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As film-screen system speed increases, so does quantum mottle. Quantum
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RADD 2501 Film Screen Systems - Overview - Film-Screen...

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