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Which of the following concerning gamma cameras are true? a. The primary purpose of the collimator is to filter out low-energy gamma rays b. Photo multipliers convert light into photo electrons c. The pulse height analyser reduces noise d. Low-energy gamma rays result from photoelectric absorption in the crystal and patient e. Spatial resolution can be improved by using collimators with wider holes |
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Answer» a. False. The primary function of the collimator is to delineate the gamma source. b. True. Each photo multiplier consists of a photo cathode that absorbs light and emits photo electrons. These are accelerated towards an anode and multiply on the way by colliding with dynodes. c. True. Gamma rays as a result of scatter have a low energy, which is filtered out by the pulse height analyser. d. False. Low-energy gamma rays result from Compton attenuation in the patient and crystal. e. False. Spatial resolution is improved by using collimators with narrower and longer holes |
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