| 摘要 |
In a computed tomography apparatus and a method for automatic exposure control in computed tomography scanning, an exposure controller, during a first half of a revolution of an X-ray focus around a subject, calculates an actual attenuation profile of a slice of the subject from electrical signals generated by the radiation detector in the first half of the revolution, and calculates an extrapolated attenuation profile of the slice for a second half of the revolution from the actual attenuation profile, and adjusts an operating parameter of the X-ray source, such as the tube current, to modify the radiation dose emitted by the X-ray source during the second half of the revolution dependent on the extrapolated attenuation profile. The extrapolated attenuation profile can be calculated to achieve a predetermined target pixel noise in the image for the slice currently being scanned. In a spiral scan composed of a number of such slices, respectively different target pixel noise values can be used to appropriately set a radiation dose in the scan of each slice dependent on the radiation absorption of the slice of the subject currently being scanned.
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