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Which of the following are true with regard to filtration? a. The aim of filtration is to make the beam intensity more uniform by removing the very high-energy rays b. The tube housing acts as a valuable filter c. The predominant attenuation process in a filter should be photoelectric absorption d. At 80 kV, the half-value layer (HVL) of a beam with 2.5 mm Al filtration is typically measured as 2–3 mm Al e. The thickness of copper required to reduce the intensity of an X-ray beam by a factor of 2 is greater than the required thickness of aluminium needed to have the same effect |
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Answer» a. False. Filtration aims to remove a large proportion of lower energy photons, which are mainly absorbed by the patient and do not contribute to the image. b. True. The tube housing forms part of the inherent filtration along with the insulating oil, glass inserts and the target itself. c. True. Photoelectric absorption is inversely proportional to photon energy and therefore attenuates the lower energy photons. d. True. Total filtration = inherent filtration + added filtration. e. False. Copper has a higher atomic number than aluminium and hence a greater photoelectric absorption efficiency. |
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