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Which of the following are true regarding the sensitivity of collimators? a. It is a measure of the fraction of total gamma rays falling on the collimator that pass through the holes to the crystalb. Increasing the number of holes increases the sensitivity c. Increasing the sensitivity reduces the patient dose d. Narrower holes result in increased sensitivity e. Longer holes reduce sensitivity |
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Answer» a. True. b. True. Increasing the number of holes results in a higher fraction of gamma rays passing through the collimator. c. True. The higher the sensitivity, i.e. the higher the number of gamma rays passing through the collimator to form the image, the lower the amount of radio nuclide needed and hence the lower the patient’s dose, but this is usually at the expense of the resolution. d. False. Wider holes allow a higher fraction of gamma rays to pass through. e. True. Longer holes result in a narrower angle of acceptance resulting in more gamma rays being stopped by the collimator. |
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