  Aiming to measure the difference in arrival times of two coincident
gamma-photons with an accuracy in the order of 200 ps, time-of-flight positron
emission tomography systems commonly employ silicon photomultipliers (SiPMs)
and high-resolution digitization electronics, application specific integrated
circuits (ASICs). This work evaluates the performance of the TOFPET2 ASIC,
released by PETsys Electronics S.A. in 2017, dependent on its configuration
parameters in multi-channel coincidence measurements. SiPM arrays fabricated by
different vendors (KETEK, SensL, Hamamatsu, Broadcom) were tested in
combination with the ASIC. Scintillator arrays featuring different reflector
designs and different configurations of the TOFPET2 ASIC software parameters
were evaluated. The benchtop setup used is provided with the TOFPET2 ASIC
evaluation kit by PETsys Electronics S.A.. Compared to existing studies
featuring the TOFPET2 ASIC, multi-channel performance results dependent on a
larger set of ASIC configuration parameters were obtained that have not been
reported to this extend so far. The ASIC shows promising CRTs down to 219.9 ps
in combination with two Hamamatsu S14161-3050-HS-08 SiPM arrays (128 channels
read out, energy resolution 13.08 %) and 216.1 ps in combination with two
Broadcom AFBR-S4N44P643S SiPM arrays (32 channels read out, energy resolution
9.46 %). The length of the trigger delay of the dark count suppression scheme
has an impact on the ASIC performance. The integrator gain configuration has
been investigated and allows an improvement of the energy resolution. Measuring
up to the time-of-flight performance of state-of-the-art positron emission
tomography (ToF-PET) systems while providing a uniform and stable readout for
multiple channels at the same time, the TOFPET2 ASIC is treated as promising
candidate for the integration in future ToF-PET systems.
