Parallel readout electronics and data acquisition for SSPM-based PET detectors

Objectives To improve the overall performance of a solid-state photomultiplier (SSPM) array based PET detector.

Methods Each SSPM inside a 4x4 SSPM array (SensL SPMArray 4, ~60 ns rise time) is read out independently through time-based front-end electronics that outputs timing and energy dependent digital timing pulses. Without signal-multiplexing, it leads to enhanced signal-noise-ratio. All event selections and event timing, energy and interaction position calculations are done by a TDC implemented inside an FPGA.

Results A prototyping 8-channel 0.35um ASIC has been designed and developed for this study. Its shows excellent linear dynamic region up to 1000pC, ~100ps (FWHM) intrinsic timing resolution, and <1.0% 511 keV energy resolution. Data acquisition has been developed and evaluated. Signals from each ASIC are processed by a detector-level FPGA to provide timings and energies from multiple SSPMs; the corresponding overall event timing and energy are calculated based on different algorithms (detailed in another abstract); events are selected based on coincidence and handled by a system-level FPGA. Initial results acquired by the new electronics from a 1.9x1.9x30 mm LYSO coupled to 4 SSPMs show better than 3 ns timing resolution (single-end readout of a long crystal), compared to ~7 ns measured from a conventional signal-multiplexing readout. In addition, the new electronics provides better SNR that leads to improved crystal identification accuracy. Both new readout electronics and data acquisition are scalable for different detector numbers and system configurations. One prototype readout and acquisition system has been built and under test - it will be suitable for a DOI measurement capable PET system that demands excellent SNR since it employs scintillators of small cross-section area and long length for high imaging resolution and sensitivity.

Conclusions Implemented low-cost parallel readout electronics and data acquisition provide flexible signal processing capability and significantly improved detector performance. Results from a PET system will be presented