Quantitative Evaluation of a Dual Energy CT System

We have evaluated the accuracy of CT numbers produced by a prototype dual energy system. Solutions of known composition were scanned in simple cylindrical phantoms and the observed CT values in synthetic monochromatic images were compared with the expected values computed from published cross-section data. Although accuracy varied with both the composition of the solution and the energy selected for the synthetic monoenergetic image, for the solutions used the inaccuracy was less than the uncertainty of the photon cross-section data at 80 and 100 keV. Virtually no cupping artifact was present in the monoenergetic images.