A study of external end-shields for PET

The effect of external end-shields in screening radiation from outside the Field of View (FOV) was studied by phantom measurements and confirmed by Monte Carlo simulation of the ECAT EXACT HR+. Accidental coincidence rates were measured with a standard calibration cylinder placed outside the FOV with and without one of several external end shields. These measurements were in excellent agreement with the Monte-Carlo simulation, which included details, such as the count rate as a function of the ring number.