A radiation detector module (10) for use in a time-of-flight positron emission tomography (TOF-PET) scanner (8) generates a trigger signal indicative of a detected radiation event. A timing circuit (22) including a first time-to-digital converter (TDC) (30) and a second TDC (31) is configured to output a corrected timestamp for the detected radiation event based on a first timestamp determined by the first TDC (30) and a second timestamp determined by the second TDC (31). The first TDC is synchronized to a first reference clock signal (40, 53) and the second TDC is synchronized to a second reference clock signal (42, 54), the first and second reference clock signals being asynchronous.