| 摘要 |
PROBLEM TO BE SOLVED: To solve such a problem that photographing time becomes long since photographing on a low tube voltage photographing side is performed only by a tube current considerably smaller than an allowable value and only the images of image quality deteriorated by the blurring of movement are obtained for a part with the movement, while photographing is performed twice without changing a filament current value in order to shorten the time interval of two images photographed by changing a tube voltage for the same photographing position as much as possible in photographing by a dual energy subtraction method. SOLUTION: By using a triode X-ray tube 11, a filament current is set to a current value for making an allowable maximum current flow during low tube voltage photographing. During high tube voltage photographing, a negative voltage is applied to a grid 9 by a grid voltage control part 10 and control is performed so that the current becomes equal to or less than the allowable maximum current to a high tube voltage. During the low tube voltage photographing, the voltage to be applied to the grid 9 is turned to 0 and the allowable maximum current to the low tube voltage is made to flow. COPYRIGHT: (C)2008,JPO&INPIT
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