How to meet the 10 ps Coincidence Timing Resolution PET challenge

Abstract

A new challenge for time-of-flight (TOF) Positron Emission Tomography (PET) is achieving 10 ps Coincidence Timing Resolution (CTR). Such a short CTR would enable a 20-fold higher TOF-related effective sensitivity gain (TOF-gain) and direct reconstruction in PET imaging. Ultrashort CTR greatly benefits brain PET imaging because owing to the relatively small size of human head, TOF-gain only begins to be significant for CTR < 150 ps. The Brain PET (BET) consortium evaluates the potential for achieving 10 ps CTR using an updated Monte Carlo modeling program (MCPET3). This new version includes the ability to set a constant refractive index at each scintillator segment face to model the effects of optical index coupling glues. In addition, the new version provides a simple method for evaluating the effect of Cherenkov photons on the CTR. The latest modeling results are compared to recent world-record experimental CTR with good agreement and only a few adjustable parameters. The results indicate that 50 ps CTR is likely to be attained in the near future, but achieving 10 ps CTR will require a number of substantial improvements in PET detector blocks technology. Based on our simulations, we estimate that in order to achieve the 10 ps CTR a 20-fold increase in scintillator intensity (photons/ps) is required, along with additional improvements in single photon timing resolution.