1. A method to generate a nuclear medicine patient image reconstructed from an average of multiple subsets of acquired counts of a patient dataset, having an image quality characteristic aligned with that of a corresponding nuclear medicine image obtained from a single reconstruction of all counts of the patient dataset, comprising: in a processor, automatically using a phantom dataset acquisition to determine an appropriate post-processing step necessary to align the image quality characteristic in order to produce a desired alignment of the image quality characteristic, by: performing an image reconstruction using the whole phantom dataset with a reconstruction algorithm to generate a phantom whole-dataset image; calculating the image quality characteristic for the phantom whole-dataset image; temporally dividing the phantom dataset into subsets of phantom image data; reconstructing each phantom data subset into a data-subset image using the reconstruction algorithm; generating a combined phantom image by averaging the image data of the phantom data-subset images; deriving a post-processing step that when applied to the combined phantom image, provides a value of the image quality characteristic aligned with that of the whole-dataset image; in said processor, generating a combined patient image by averaging image data of a plurality of patient data-subset images; and in said processor, applying the derived post-processing step to the combined patient image, thereby obtaining a post-processed image, and making said post-processed image available at an output of the processor in electronic form.