1. A method for detecting the onset of a gamma interaction in a positron emission tomography (PET) imaging system, comprising: obtaining a sequence of a plurality of primary trigger event timings; applying a predetermined weighting factor to each of the plurality of primary trigger event timings to obtain a sequence of weighted primary trigger event timings; combining said sequence of weighted primary trigger event timings to obtain an overall event trigger timing; and determining the onset of a gamma interaction in said PET imaging system based at least on said overall event trigger timing.