1. A method for enhancing signal-to-noise characteristics of an image, the steps of the method comprising: a) providing an image to be enhanced; b) producing synthesized image data by performing a forward projection of the provided image; c) producing a prior image by filtering the provided image such that noise from the provided image is substantially suppressed in the prior image; d) subtracting the provided image and the prior image to produce a sparsified image; and e) reconstructing an enhanced image using the sparsified image, the provided image, and the synthesized image data, the enhanced image having a higher signal-to-noise ratio than the provided image.