An x-ray computed tomography system , comprising: a gantry configured to move to different orientations and generate x-ray data which includes image projection data at a plurality of the orientations; a plurality of elements connected to the gantry which cause x-ray attenuation of the generated projection data, and the plurality of elements include an x-ray source , an x-ray filter , a shutter/collimator , an x-ray detector and an anti-scatter grid ; one or more processors programmed to: receiving the generated x-ray data which includes image projection data at each of a plurality of gantry orientations around an imaging region; wherein the generated x-ray data includes measurements of attenuation attributable to a imaged subject and measurements of attenuation attributable to the plurality of elements, and the measurements of attenuation attributable to the plurality of elements changes with the plurality of gantry orientations, decomposing the received image projection data to derive relative positions of the plurality of elements at one or more gantry orientations, each of the elements causing x-ray attenuation attributable to the elements in the received image projection data, and generating a correction of the measured attenuations based on the relative positions of the plurality of elements. a gantry configured to move to different orientations and generate x-ray data which includes image projection data at a plurality of the orientations; a plurality of elements connected to the gantry which cause x-ray attenuation of the generated projection data, and the plurality of elements include an x-ray source , an x-ray filter , a shutter/collimator , an x-ray detector and an anti-scatter grid ; one or more processors programmed to: receiving the generated x-ray data which includes image projection data at each of a plurality of gantry orientations around an imaging region; wherein the generated x-ray data includes measurements of attenuation attributable to a imaged subject and measurements of attenuation attributable to the plurality of elements, and the measurements of attenuation attributable to the plurality of elements changes with the plurality of gantry orientations, decomposing the received image projection data to derive relative positions of the plurality of elements at one or more gantry orientations, each of the elements causing x-ray attenuation attributable to the elements in the received image projection data, and generating a correction of the measured attenuations based on the relative positions of the plurality of elements. receiving the generated x-ray data which includes image projection data at each of a plurality of gantry orientations around an imaging region; wherein the generated x-ray data includes measurements of attenuation attributable to a imaged subject and measurements of attenuation attributable to the plurality of elements, and the measurements of attenuation attributable to the plurality of elements changes with the plurality of gantry orientations, decomposing the received image projection data to derive relative positions of the plurality of elements at one or more gantry orientations, each of the elements causing x-ray attenuation attributable to the elements in the received image projection data, and generating a correction of the measured attenuations based on the relative positions of the plurality of elements. <EOS>