1. A method of generating an image, comprising the steps of: a) generating a combination weight value for measured projection data at each of measured projections based upon at least a predetermined noise model and a predetermined window function; and b) applying the combination weight values using the measured projection data in one of predetermined iterative reconstruction techniques while an image is being iteratively reconstructed, wherein the predetermined noise model is defined by V=(g I+Ve/I)/I, where the I is a measured signal while Ve and g are respectively the electronic noise variance and the detector gain that is function of channels, segments, a data acquisition system and or collimation.