1. A method, comprising: estimating a local noise value for one or more voxels of a spectral image of a set of spectral images corresponding to different energy ranges, producing a noise model for the spectral image; estimating local structure models for a voxel of the spectral image based on a corresponding noise model; selecting one of the local structure models for the voxel of the spectral image based on predetermined model selection criteria; and de-noising the voxel of each spectral image of the set of spectral images based on the selected local structure model by replacing a value of the voxel of each spectral image with a value estimated based on the selected local structure model, wherein a plurality of the voxels of a plurality of spectral images in the set of spectral images are de-noised, producing a set of de-noised spectral images.