Comparison of Three Approaches for Timing Optimization of a Dual Layer LSO-APD Small Animal PET Scanner

The application of avalanche photodiodes (APDs) for the readout of scintillation crystals offers the possibility of using compact detector modules in positron emission tomography. Good timing resolution is more challenging with APDs due to their lower gain and larger rise time in comparison to photomultiplier tubes. This study examined the different factors influencing time resolution and investigated three approaches for optimizing the time resolution of a dual layer LSO-APD small animal PET scanner. The used PET scanner (MADPET-II) features individual readout of LSO scintillation crystals (2×2 ×6mm3 front layer and 2×2×8 mm3 back layer) by APD arrays. The system consists of 1152 LSO-APD channels arranged in a dual layer detector ring. For the purpose of this study different approaches for optimizing the time resolution were compared: A) Measurement and correction for amplitude walk in the analog part of the acquisition electronics. B) Determination of interchannel delays by two methods: B1) Measurement using a timing alignment probe. B2) Software approach based on an iterative algorithm.