Evaluation of the FlexToT ASIC on the Readout of SiPM Matrices and Scintillators for PET

We have designed FlexToT, a flexible application specific integrated circuit (ASIC) using time-over-threshold (ToT) techniques for the readout of silicon photomultiplier (SiPM) arrays in positron emission tomography (PET) detectors. The FlexToT ASIC accommodates 16 independent channels in a small die size (2.93 mm by 2.54 mm) with low power consumption (10 mW per channel), providing output signals whose duration is proportional to the current amplitude at its inputs. The threshold, gain and other parameters can be independently set for each channel in a flexible configuration that can be tailored to different applications and devices. Herein we present the results on the evaluation of the FlexToT ASIC operating as front-end electronics for SiPM arrays S11828-3344M from Hamamatsu (Japan) coupled to LYSO:Ce scintillators in a simple PET tomograph demonstrator. Each detector block is composed of a LYSO:Ce matrix coupled to 4 SiPM arrays in a 2x2 mosaic, totaling 64 pixels (8x8) which are read out by 4 FlexToT ASICs. Using this demonstrator we have obtained PET images of Na-22 point sources with spatial resolutions better than 2 mm full width at half maximum (FWHM), validating our design of the FlexToT ASIC on the readout of SiPM matrices and scintillators in PET applications.