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The Effects of Intensifying Screens on Density

When X-ray light passes through any object, the object's properties influence the light. This is especially true in X-ray technology, or radiography. When technicians send X-ray light, or gamma rays, through your body, the rays also move through intensifying screens contained in the X-ray film cartridge. Intensifying screens are meant to enhance the visibility of the organisms being assessed, while (in varying degrees) darkening everything else. Intensifying screens influence the density, or visual integrity, of X-ray images.

  1. Kinds of Screens

    • Intensifying screens are contained in X-ray film emulsions. According to Eastman Kodak, intensifying screens come in several varieties, each one producing a specific influence on X-ray density. However, other conditions also factor in to X-ray imaging: the tube current of the light bulb, the total amount of emitted radiation and the exposure time. The intensifying effect varies considerably with the conditions of screen exposure, according to the Radiological Society of America (RSNA). Although density differences are desirable in X-rays, too much density darkens the detail needed for quality X-ray assessment.

    Fluorescent

    • Fluorescent intensifying screens are used with "screen type films," according to Fuji Film. When X-rays contact fluorescent screens, materials called phosphors emit light in their unique regions of the light spectrum. Match phosphors with the light sensitivity of an X-ray film, and the fluorescent screen intensifies the light factor by 10 to 200 times, according to Fuji. This intensification reduces the exposure time needed to produce an acceptable image. However, the phosphor influence in fluorescent screens provides insufficient image definition when such an X-ray is aimed at identifying very minute medical defects in the human body.

    Lead

    • Lead intensifying screens are used with "non-screen type films," according to Fuji Film. Screens composed of lead emit electrons when struck by high-energy X-ray light. Lead foil emulsions do not affect light's penetration through the screen, but they intensify that light between two to three times, according to Fuji Film. The more radiation energy is used, the thicker a lead intensifying screen must be to produce the best X-ray result. Front and back lead foils are generally between 0.1 and 0.3 millimeters thick.

    Fluorometallic

    • Fluorometallic screens form a hybrid of lead and fluorescent properties for use in both screen and non-screen films. A fluorometallic intensifying screen contains lead foil covered in phosphor. In screen films, fluorometallic, such as fluorescent, screens intensify X-ray light by five to 30 times. In non-screen films, such as lead, fluorometallic screens intensify X-ray light by 30 to 150 times. Fuji claims that fluorometallic intensifying screens have a shorter shelf life due to their versatile properties. Put simply, they burn out sooner because they flex to the capabilities of any X-ray film.

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