| 摘要 |
PROBLEM TO BE SOLVED: To easily obtain image data in the optimum range at all times in a method for detecting X-ray beam quantity and in an X-ray CT apparatus. SOLUTION: In this method for detecting X-ray beam quantity, an X-ray beam is irradiated for a subject 100 from an X-ray tube 40, the X-ray beam passing through the subject is detected, the detected output is integrated by integrators 811 to 81n to generate an X-ray beam quantity detection voltage, and the output is A/D converted by an A/D converter 83 to obtain X-ray beam quantity detection data. Time constants of the integrators 811 to 81n are changed in accordance with one or two or more imaging parameters of a tube voltage kV of the X-ray tube, a tube current mA, a detection width Thic in axis direction of the subject, and X-ray irradiation time Sec for the subject which are imaging parameters to generate an X-ray beam quantity detection voltage in the optimum dynamic range which does not exceed the range for the A/D converter 83 per channel.
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