An x-ray imaging system, comprising: an x-ray source system for generating a high energy x-ray beam and a low energy x-ray beam; a sample holder for rotating a sample in the high energy x-ray beam and the low energy x-ray beam from the x-ray source system to perform a low-energy scan and a high-energy scan of the sample; a detector system for detecting the high energy x-ray beam and the low energy x-ray beam after transmission through the sample to generate projection data; a computer system generating a low-energy reconstructed tomographic volume data set from the low-energy scan and generating a high-energy reconstructed tomographic volume data set from the high-energy scan in the computer system from the projection data, and rendering slice views from the low-energy and high-energy reconstructed tomographic volume data sets and presenting a mathematically combined synthetic slice characterized in that the computer system presents a slice selection means from the low-energy and high-energy reconstructed tomographic volume data sets; and renders a low-energy slice view from the low-energy reconstructed tomographic volume data set and a high-energy slice view from the high-energy reconstructed tomographic volume data set for the same region of the sample, in response to user selection of a slice view within slice selection means. creates a two-dimensional histogram of high-energy x-ray pixel intensity values versus low-energy x-ray pixel intensity values based on the selected slice in which intensity of points on the histogram is associated with the count of voxels with the low-energy and high-energy pixel intensity values respectively pixel intensity; and displays the histogram. an x-ray source system for generating a high energy x-ray beam and a low energy x-ray beam; a sample holder for rotating a sample in the high energy x-ray beam and the low energy x-ray beam from the x-ray source system to perform a low-energy scan and a high-energy scan of the sample; a detector system for detecting the high energy x-ray beam and the low energy x-ray beam after transmission through the sample to generate projection data; a computer system generating a low-energy reconstructed tomographic volume data set from the low-energy scan and generating a high-energy reconstructed tomographic volume data set from the high-energy scan in the computer system from the projection data, and rendering slice views from the low-energy and high-energy reconstructed tomographic volume data sets and presenting a mathematically combined synthetic slice characterized in that the computer system presents a slice selection means from the low-energy and high-energy reconstructed tomographic volume data sets; and renders a low-energy slice view from the low-energy reconstructed tomographic volume data set and a high-energy slice view from the high-energy reconstructed tomographic volume data set for the same region of the sample, in response to user selection of a slice view within slice selection means. creates a two-dimensional histogram of high-energy x-ray pixel intensity values versus low-energy x-ray pixel intensity values based on the selected slice in which intensity of points on the histogram is associated with the count of voxels with the low-energy and high-energy pixel intensity values respectively pixel intensity; and displays the histogram.