A CT system includes a rotatable gantry having an opening to receive an object to be scanned, a high-voltage generator, an x-ray tube positioned on the gantry to generate x-rays through the opening, and a pixelated detector positioned on the gantry to receive the x-rays. The system includes a computer programmed to cause the x-ray tube to generate x-rays, at a given high-voltage generator voltage (kV), toward a sub-set of detector pixels when no object is present within the opening, measure an output of the sub-set of detector pixels for a given number of views during the x-ray generation and for a total integration time, and determine a calibration factor based on the measured output and based on a generator feedback current measured during the total integration time.
