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Concerning the focal spot: a. Its size may be estimated using a slit camera b. Its size may be estimated using a star test pattern c. A smaller anode angle reduces the size of the effective focal spot d. A larger anode angle is useful for general radiography e. The size of the actual focal spot is partly determined by the length of the cathode filament |
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Answer» a. True. A slit camera consists of a metal plate with a slit positioned between the tube and the image receptor. One dimension of the focal spot can be calculated from magnification of the slit image. This is then repeated for the other dimension with the slit perpendicular to its original position. b. True. This involves a test object with markings at a set distance apart with which an image is produced of a certain magnification. The degree of blurring of the markings in the image can be used to estimate focal spot size, as it is greater with a larger focal spot. c. True. d. True. This allows greater tube loading and higher output, which is often necessary when imaging larger parts of the body. It also increases the size of the field coverage at short focal spot-to-image distances. e. True. It is also determined by the width of the focusing cup at the cathode. |
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