Digital silicon photomultiplier for TOF-PET

A detector pixel for use in conjunction with a scintillator that converts a radiation particle to a burst of light, the detector pixel comprising:

• an array of detector cells, each detector cell including a photodiode biased in a breakdown region and digital circuitry coupled with the photodiode, the digital circuitry being configured to output a first digital value in a quiescent state and a second digital value responsive to detection of a photon by the photodiode;
• digital triggering circuitry configured to output a trigger signal indicative of a start of an integration time period responsive to a selected number of one or more of the detector cells transitioning from the first digital value to the second digital value;
• readout digital circuitry that accumulates a count of a number of transitions of detector cells of the array of detector cells from outputting the first digital value to outputting the second digital value over the integration time period;
• a proportional photodiode configured to produce an analog photocurrent proportional to a flux of photons impinging upon the detector pixel;
• and
• digital time stamp circuitry connected to the array of detector cells to create a timestamp based on a time of the trigger signal that indicates a time of receipt of the flux of photons.