New Approaches for Improvement of Time-of-Flight PET

Full text: Advances in detector technology led to the construction of commercial time of flight (TOF) positron emission tomography (PET) devices, resulting in enhanced image contrast, lower patient's dose and shorter examination times. Commercial TOF-PET scanners with coincidence time resolutions of 500-600 ps FWHM are already available. Goal of this work is the improvement of time resolution for TOF-PET using Silicon photomultipliers (SiPM) and the Cherenkov effect. Along with many comparable features to ordinary vacuum photomultipliers, SiPMs are considerably smaller in size and insensitive to magnetic fields, which makes them usable for hybrid devices such as PET-NMR. The use of the Cherenkov effect at gamma energies of 511 keV should help to improve time resolution of PET detectors dramatically. As Cherenkov photons are emitted almost instantaneously, compared to scintillation photons, the ability to detect and distinguish them from the scintillation signals, provide precise time stamps for TOF. First measurements using PMTs have been accomplished successfully. For the development of a future TOF-PET prototype, Monte Carlo (MC) simulations using the framework GATE and SLitrani are performed to optimise the experimental setup (pixel size, material, arrangement of the SiPMs). The simulated raw data have been analysed by self-developed software and first sinograms have been calculated. In this work the results of recent measurements on the time resolution of our setup, calculations and measurements related to the detection of Cherenkov photons at energies of 511 keV, and latest results of MC simulations on new detector designs, will be presented. (author)