Digital Upgrade of a PSPMT-based Pet Detector for High Resolution Pre-Clinical Application

The precision of positron emission tomography (PET) as a quantitative imaging modality in the study of metabolic processes in preclinical imaging application depends on specific features in PET detectors such as efficient, accurate, and fast detection capability of gamma rays emitted from the region of interest (ROI) inside the object under investigation. The aim of this work is to upgrade a PSPMT-based PET detector to a flexible and scalable modular design that can be easily configured for optimal performance in a wide range of imaging tasks. The upgrade encompasses the substitution of the readout circuit with a sigma-delta analog-to-digital converter (ΣΔ-ADC) circuit, as well as the integration of a dedicated data acquisition unit (DAQ) for the purpose of digital signal processing and data acquisition. To assess performance, three scintillation arrays with distinct characteristics were employed: a 5x5 array of 2 mm crystals with a Teflon reflector, a 10x10 array of 1 mm crystals with an ESR reflector, and a 16x16 array of 0.97 mm crystals with a Toray reflector. The detectors are characterized in terms of the energy resolution calculated on the summed output of the entire array and the flood histogram parameters. Measured over each entire block, the data show that an energy resolution of 21.1%, 21.8%, and 31.3% at 511 keV photopeak of
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Na is achieved for the 5x5, 10x10, and 16x16 arrays respectively. For crystal identification, almost all the crystals are resolved and identified. The initial findings of the results are promising and can serve as a foundation for future investigations of ultra-high resolution scintillation arrays. The PET modular design currently under development is intended to function as a plug-and-play system for use in dedicated high-resolution imaging applications, including but not limited to imaging of human finger joints and small animal preclinical imaging.