Multichannel low noise high frequency SiPM readout of scintillation crystal arrays

Low noise, high frequency (LNHF) electronic readout for silicon photomultiplier (SiPM)-based time-of-flight positron emission tomography (TOF-PET) detectors preserves fast signal response available from the capacitively coupled terminal of Geiger mode cells and minimizes the influence of electronic noise jitter to optimize time response. By facilitating fast impulse response for large area SiPMs, LNHF readout allows detectors to optimally exploit fast luminescence signatures and prompt optical phenomena for next-generation detector designs that aim to advance coincidence time resolution (CTR) for TOF-PET. Recent studies have shown LNHF circuits that provide the benefits of this readout technique with smaller footprints and lower power consumption feasible for developing multichannel readout for prototyping advanced PET detector designs. In this work, we integrate these circuits into multichannel LNHF electronic readout boards and evaluate their ability to translate state-of-the-art CTR demonstrated in single crystal benchtop experiments into measurements with scintillation crystal arrays. Two types of multichannel readout boards were fabricated, one type with sixteen channels, each with separate energy and timing readout, and a second type with a four-to-one multiplexing of timing channels to explore the impact of further reducing power consumption and channel count. Single pixel CTR studies with the sixteen channel development board yielded identical results to those previously achieved with single channel implementations of the same readout topology. CTR measurements with 20 mm length LYSO:Ce,Ca and bismuth germanate (BGO) crystal arrays demonstrated global CTR of 134 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"> <mml:mrow> <mml:mo>±</mml:mo> </mml:mrow> </mml:math> 1 and 255 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"> <mml:mrow> <mml:mo>±</mml:mo> </mml:mrow> </mml:math> 16 ps FWHM, respectively, including both photoelectric and inter-crystal Compton scatter events. Timing performance was preserved in the multiplexed circuit topology with LYSO:Ce,Ca crystal arrays, and dual threshold timing corrections applied with the multiplexing circuit and 20 mm length BGO crystal array further improved global CTR to 233 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m3"> <mml:mrow> <mml:mo>±</mml:mo> </mml:mrow> </mml:math> 13 ps FWHM. This multichannel readout board is a test bed for novel detector concepts to further improve achievable CTR. We also present a further miniaturized readout scheme in a modular circuit block which fits within the area of a 4 × 4 SiPM tile array, in an edge-mounted readout configuration for PET detector module readout. Overall, we show that state-of-the-art CTR demonstrated with single channel electronic readout can be translated into array readout for advanced PET detector designs.