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Pushing PET detector performance to the physical limits

The performance of a PET detector is characterized by its spatial resolution, timing resolution, energy resolution, and detection efficiency. Each of these factors has a major influence on the quality of the final PET image. Since the primary signal consists of a small number of optical photons created upon the absorption of an annihilation photon within the scintillation crystal, it is essential to use the best possible scintillator. SUBLIMA aims to maximize the quality of the primary optical signal by choosing the best scintillation material and optimizing the crystal geometry.

Furthermore, a new, fast, and highly sensitive type of solid-state light sensor called silicon photomultiplier (SiPM) will be used to detect the scintillation photons. Whereas conventional PET systems make use of only 10-12% of these photons, SUBLIMA aims to detect over 40% of the scintillation photons, both by optimizing the sensitivity of the light sensors themselves and by introducing novel optical technology for coupling the scintillation photons into the light sensors with minimum losses due to differences in refractive index. In addition, the readout geometry will allow determination of, and correction for, the depth-of-interaction (DOI) of the annihilation photon.

The analogue signal path must be kept as short as possible to avoid interference, especially within gradient- and RF-field environment of the MR. As part of a novel digital readout architecture, dedicated readout chips for digitization of the detector signals will be developed that will be placed directly onto the back of the light sensors using an optimized inter­connection scheme. Furthermore, a digital signal processing platform located inside each detector module will enable real-time extraction and DOI correction of position, time and energy information in a massive parallel manner. In this way, SUBLIMA aims to realize a highly accurate and versatile digital PET detector technology that can be adapted to achieve maximum performance in different applications.