An iterative dual energy CT reconstruction method for a K-edge contrast material

We present and evaluate an iterative dual energy CT reconstruction algorithm for a K-edge contrast material in microCT imaging. This allows improved discrimination of contrast enhanced structures such as vasculature from surrounding bony structures. The energy dependence of the attenuation is modeled by decomposing the linear attenuation coefficient into three basis functions. Any material without a K-edge in the imaging energy range can be modeled by two basis functions describing the Compton scatter and the photoelectric effect respectively. A K-edge material is described by using its mass attenuation coefficient as third basis function. During reconstruction the basis function coefficients are determined for each voxel of the image by maximizing the likelihood of the data. The relative weights of the Compton and photoelectric components are constrained to those of expected materials to reduce the number of unknowns to two per voxel. The proposed method is validated on simulated and real microCT projections. The presented method was found to perform better than a typical post-reconstruction approach with respect to beam-hardening and noise at the expense of increased computation time.