| abstract |
In a radiation detector (10) for a time of flight positron emission tomography (PET) scanner (2), a radiation sensitive member (20) generates a signal (22) indicative of a radiation detection event. A time to digital converter (34) includes digital delay elements (40) operatively interconnected as a ring oscillator (36, 36') and readout circuitry (50, 52, 60, 82, 84, 86, 88) configured to generate a timestamp for the radiation detection event based at least on a state of the ring oscillator when the signal is generated. Delay trim elements (46) operatively connected to the digital delay elements set a substantially common delay for the digital delay elements. Additionally or alternatively, the digital delay elements (40) include readout buffers (48') having transition times substantially longer than a delay of the digital delay elements, analog to digital converters (82, 84) digitize values of the delay elements, and decoding circuitry (86, 88) computes the state of the ring oscillator (36') based on the digitized values. |