An imaging system (2) having a scalable event processing architecture includes a plurality of detector modules (4) arranged around an associated imaging region (8) to detect radiation events emitted from a subject disposed within the imaging region (8); a plurality of sets of processing elements (6), each set including processing elements of at least one of the plurality of radiation detector modules (4), each processing element (6) time-stamping an associated detected radiation events; and inserting the time-stamped event into a chronological position within a data stream (10) of events; and coincident detecting circuitry (22, 54) that receives the chronologically ordered stream of events and detects coincident pairs of events for use in reconstructing one or more associated images of the object.