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Decreasing the tube voltage (kV) results in which of the following? a. It reduces the number of electrons colliding with the target b. It reduces the photon fluence c. It reduces the beam intensity d. It results in the increase of the half-value layer (HVL) for a given material e. The rate of photoelectric attenuation increases more than the rate of Compton attenuation |
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Answer» a. False. The number of electrons (tube current, mA) is controlled by the filament voltage. b. True. Although the number of filament electrons produced are unaffected by kV, the number of photons created in the target per electron decreases with a reduction in kV, e.g. number of photos at 10 mA, 90 kV > number of photons at 10 mA, 60 kV. c. True. Beam intensity is the total amount of energy per unit area passing through per unit time. d. False. HVL reduces as beam penetration reduces. e. True. Due to a reduction in photon energy, the rate of photoelectric attenuation increases more than the rate of Compton attenuation. |
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