1. A method of generating a filter for a nuclear medicine imaging system, the filter for selecting valid detected radiation events for image processing, the method comprising: providing a dataset indicative of a plurality of emitted radiation events occurring over a predetermined period of time; generating signals representative of the response of a detector to the dataset of the plurality of emitted radiation events; determining a correlation pattern based on a correlation of a plurality of signals resulting from the response of the detector for each of a plurality of single radiation events in the dataset; and generating a filter based on the correlation pattern.