1. A computer-implemented method of performing a security inspection of a container including a plurality of objects therein using a computing device including at least one processor coupled to a memory device, said method comprising: irradiating the container with polychromatic x-rays; reconstructing, using the computing device, a four-dimensional (4-D) voxelized representation of a plurality of scatter cross-sections within the container, wherein the 4-D voxelized representation includes a plurality of voxels, a first three dimensions represent a spatial location of each voxel of the plurality of voxels, and a fourth dimension represents a plurality of momentum transfer values defining a momentum transfer spectrum of the container; generating at least one three-dimensional (3-D) image by determining a single value at each voxel of the plurality of voxels as a function of the momentum transfer spectrum; segmenting the plurality of voxels into a plurality of segments of contiguous voxels, wherein each segment of the plurality of segments includes a plurality of contiguous voxels, wherein at least a portion of the plurality of segments at least partially maps onto at least one object of the plurality of objects; computing one or more aggregated momentum transfer spectra over the at least a portion of the plurality of segments by using at least a portion of the plurality of contiguous voxels as guides for aggregation; classifying the one or more aggregated momentum transfer spectra as one of threat and non-threat; and distinguishing the at least one object as one of a threat segment and a non-threat segment based on the one or more aggregated momentum transfer spectra.