1. A system comprising a computing device and at least one program module that are together configured for performing actions comprising: identifying an artifact in an image, where the artifact results from an impurity, and where the identifying comprises: determining, with respect to an estimated projection geometry, a function space of possible impurity artifacts, identifying a minimum distance between an estimated artifact formation model and one of the possible impurity artifacts of the determined function space, and constructing, based on the determined function space and on the identified minimum distance, a dust removal solution; and removing, based on the constructed dust removal solution, the identified artifact from the image.