Programmable Integrated Front-End for SiPM / PMT PET Detectors with Continuous Scintillator Crystal

Research areas:
Authors:
Herrero-Bosh, V.; Monzo, J. M.; Ros, A.; Aliaga, R. J.; González, A.; Montoliu, C.; Colom-Palero, R. J.; Benlloch, J. M.
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2012
Article
JINST
7
December

 

Abstract:
Detectors based on continuous scintillator crystals and SiPM arrays have demonstrated to be a high performance alternative to position sensitive PMT. However SiPM arrays introduce new problems compared to former PMT technology such as a higher dark count or the lack of a common trigger signal. In order to overcome most of these problems and provide a generic and expandable solution for implementing any size SiPM array / PMT detectors, an integrated front-end AMIC was presented. The underlying idea in AMIC architecture is to calculate the moments of the detected light distribution in an analog fashion. Due to the additive nature of the moment calculation, the operation can be carried out on a single device or split it into several devices, adding the partial results afterwards. Up to eight different moments can be calculated, thus obtaining information about energy, x/y position, depth of interaction or any other parameter related to the light distribution of the detected event. A new integrated front-end device AMIC2GR has been developed which improves several features of the original AMIC. SiPM compatibility has been enhanced in order to expand bandwidth and increase speed, which are similar now to those obtained with PMT. A lower noise has been achieved which yields SNR > 60 dB. Precision of the coefficients applied to the detector output currents have been improved (almost 8 effective bits) as well as gain dispersion among inputs which is kept within 3.5% without calibration. AMIC2GR improved performance allows to deal with the problems introduced by SiPM arrays. First of all, its implementation equalizes the delay among inputs which allows obtaining a common trigger signal from one of the computational blocks designed for moment calculations. Dark count effects can also be mitigated by reducing SiPM voltage supply since output currents are amplified close to the detector by AMIC2GR preamplifiers stage. Also inhomogeneity among SiPMs throughout the array can be equalized using the programmable gain coefficients inside the computational blocks. Extensive experimental measurements have been carried out on a dual detector PET set-up which have shown comparable results to those obtained in with PMT.

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