Design of high resolution PET detectors using avalanche photodiodes

We describe new high-resolution depth-of-interaction (DOI) PET detector designs based on avalanche photodiodes (APDs). With the development of APDs which utilize thin drift regions to speed response time, these detectors promise improved timing performance relative to previously reported APD-based DOI detectors. The new designs also offer improved decoding of smaller crystals at room temperature through the use of a combination of position-sensitive APDs and pixellated APDs. The number of read-out channels for these designs is kept much smaller than the number of scintillator crystals by ganging together APD outputs in an encoding pattern which still allows for the correct identification of the crystal-of-interaction