Timing-optimized FBK Silicon Photomultipliers for a modular ToF-PET scanner: the PETVision

Positron Emission Tomography (PET) is one of the leading methodologies in medical imaging for cancer diagnosis, but PET scanners present some limitations in terms of cost and performance. In recent years, Time-of-Flight PET (ToF-PET) significantly improved image reconstruction by adding to the energy used in standard PET machines, the time of arrival information of the two 511 keV annihilation photons. The PETVision project aims to use breakthrough findings in the ToF-PET research field to develop a highly sensitive, fully modular and cost-accessible scanner to achieve 75 ps FWHM Coincidence Time Resolution (CTR). This challenge requires a revolutionary technology change in terms of photodetectors, readout electronics and integration methodology to push the limit of the timing performance. In controlled laboratory conditions, a CTR of 96 ps FWHM has been achieved by using FBK NUV-HD-MT SiPMs 3 × 3mm2, 40μm cell size with metal masking outside the active area (M0) coupled with a 2mm×2mm×20mm co-doped LYSO:Ce:Ca crystal. A 60 ps FWHM CTR was achieved using the same device on a 2 mm × 2 mm × 3 mm crystal. These measurements have been performed using high-frequency readout electronics with high power consumption; thus, they are not scalable to multichannel systems and are impractical for realistically sized imaging systems. Therefore, much effort is being made to develop a novel, custom front-end System-on-Chip (SoC) ASIC to be coupled with these next-generation timing-optimized SiPMs and ensure high-timing performance. Preliminary results using the FastIC+ ASIC, developed at ICCUB and CERN, are extremely promising, showing a CTR of 89 ps FWHM with a 3mm co-doped LYSO:Ce:Ca crystal using a FBK NUV-HD-MT 3×3mm2 50 μm M0. Thanks to the collaboration of several universities, research centres and industries, PETVision is set to make significant advancements in detector design, photo-sensor and front-end electronics by developing an affordable, fast and precise ToF-PET scanner, enabling early cancer detection and therapy monitoring, opening the way for personalized medicine.