1. A correction method for reducing error in cone beam computed tomography images, the method comprising: generating a plurality of two-dimensional projection images of a subject from a three-dimensional multi-detector computed tomography image of the subject, which is spatially registered with a three-dimensional cone beam computed tomography image of the subject; subtracting the plurality of two-dimensional projection images from a plurality of two-dimensional cone beam projection images of the subject, resulting in a plurality of two-dimensional estimated error projections, which comprise an estimated error in the plurality of two-dimensional cone beam projection images; subtracting the plurality of two-dimensional estimated error projection images from the plurality of two-dimensional cone beam projection images to generate a plurality of two-dimensional corrected cone beam projection images; and constructing a three-dimensional corrected cone beam computed tomography image of the subject from the plurality of two-dimensional corrected cone beam projection images.