1. A method for processing images obtained by tomography or tomosynthesis, the method comprising: acquiring a plurality of 2D projection images of an object using an imaging system, the acquiring a plurality of 2D projection images of an object being defined by Rf=s wherein s is a vector of the acquired projections, R is a projection operator which models the imaging system and f is the 3D image of the object to be reconstructed with knowledge of R and s; and processing the acquired 2D projection images, wherein the processing the acquired 2D images comprises applying an iterative algorithm defined by its iteration, wherein at least one set of processed projection images is generated at each iteration, the iteration being defined so that at each iteration the 3D image of the object is a linear function of the processed 2D projection images according to the property f (n) = R p (n) wherein R is a matrix such that R Rf is a 3D image.