1. A tomographic reconstruction method for reconstructing a 3D image object corresponding to a data set, the method comprising: providing a pixon map; for each iteration step in a series of iteration steps of iterative reconstruction, determining, by a processor, an updated object by performing a combined operation including: performing an update operation for updating an input object, and performing a pixon smoothing operation for smoothing based on the pixon map; and following a last iteration, outputting, by the processor, one of the updated objects as the 3D image object.