1. A method of generating a computed tomography image comprising: acquiring a first plurality of projections at a first energy level; acquiring a second plurality of projections at a second energy level; reconstructing an image from the first plurality of projections; generating a synthesized projection from the image that corresponds to one of the second plurality of projections; comparing the synthesized projection to said one of the second plurality of projections; and modifying the image to form an updated image based on said comparing the synthesized projection to said one of the second plurality of projections.