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Regarding subject contrast in radiography, which of the following are correct?a. It depends on the thickness of the structure being imaged b. It depends on the linear attenuation coefficients of the structures being imagedc. It increases with the tube kV d. Contrast between low-atomic-number structures (e.g. fat and muscle) is strongly affected by changes in the tube kV e. Contrast between air and soft tissue is due to differences in their atomic numbers |
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Answer» a. True. It is proportional to the thickness of the imaged object. b. True. It is proportional to the difference between linear attenuation coefficients of the tissues involved. c. False. With increasing peak kV (kVp), the relative probability of the Compton effect increases, which compromises contrast. d. False. In the range of photon energies used in general radiography, the contrast between low-atomic-number tissues is low and only minimally dependent on kVp. e. False. It is due to a large difference in density. The effective atomic numbers of air and soft tissue are very similar. |
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