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: providing a processor with a phantom dataset comprising acquired data acquired from a phantom; in said processor, performing an image reconstruction using the whole phantom dataset with a reconstruction algorithm to generate a phantom whole-dataset image; in said processor, calculating the image quality characteristic for the phantom whole-dataset image; in said processor, temporally dividing the phantom dataset into subsets of phantom image data; in said processor, reconstructing each phantom data subset into a data-subset image using the reconstruction algorithm; in said processor, generating a combined phantom image by averaging the image data of the phantom data-subset images; in said processor, deriving a post-processing filter that, when applied to the combined phantom image, provides a value of the image quality characteristic aligned with that of the whole-dataset image; providing said processor with a plurality of sets of time slice data acquired from the patient; in said processor, reconstructing a respective time slice image from each of said sets of time slice data using said reconstruction algorithm in said processor, generating a combined patient image by averaging said plurality of the slice images; and in said processor, applying the derived post-processing filter 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.