Patent ID: 7224763

Claim:
A method of correcting reconstructed images, reconstructed from projection data acquired while scanning objects with a scanner including a scanner detector array, for the spectral variation in multi-energy X-ray computed tomography using at least a portion of the same acquired projection data, wherein the projection data include at least a set of low-energy projections and a set high-energy projections obtained using at least two x-ray spectra, and wherein a filter is mounted relative to at least a portion but not the whole of the detector array, comprising: A. Generating low-energy and high-energy working filter ratios respectively for each of the low-energy and high-energy projections, derived from data acquired by at least a portion of the detector array, and calculating spectral variation using low-energy and high-energy base filter ratios and the low-energy and high-energy working filter ratios; B. Calculating working high-energy CT numbers and working effective atomic numbers as a function of the low-energy and high-energy working filter ratios, the low-energy and high-energy base filter ratios, and base high-energy CT numbers and base-effective atomic numbers for a set of three reference materials; and C. Calculating scales and offsets using the working high-energy CT numbers and the working effective atomic numbers and correcting the reconstructed images using the scales and offsets.