1. A method for cone beam CT imaging of an object, the method comprising: (a) acquiring a plurality of projection images of the object by using an imaging process that uses a polychromatic x-ray source, an energy-resolving detector, and a grating system; (b) acquiring in each of the plurality of energy channels of the detector one of a plurality of projection images; (c) acquiring a plurality of projection images of the object at different view angles and perform three-dimensional (3D) computed tomography reconstructions of the object for each of the plurality of energy channels; and (d) processing the plurality of 3D reconstruction images for each of the plurality of energy channels acquired in step (c) to produce an image of the object.