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Concerning intensifying screens: a. They typically measure 1 cm in thickness b. They are usually made of calcium tung state phosphorc. They convert the pattern of X-ray intensities into one of light, which is detected by the film d. Films and screens should be matched e. A phosphor with a K-edge value similar to the mean photon energy should be selected |
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Answer» a. False. The thickness is much less, usually 1–2 mm. b. False. They are usually made of the rare earth metals such as gadolinium oxysulphide or lanthanum oxy bromide. c. True. To produce an image on film without a screen would require high levels of radiation due to its relative insensitivity. Screens are used to reduce the dose required to produce an adequate image. d. True. The colour of the emitted light will vary depending on the phosphor used within the screen. The film should therefore be sensitive to the emitted light to ensure that the image is obtained. For example, gadolinium oxysulphide emits green light, whereas lanthanum oxy bromide emits blue light. e. True. This ensures that there is increased attenuation of the radiation spectrum, whose intensity may then be converted into one of light and thus represented as an image on the radio graphic film. |
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