Signal to noise ratio in simulations of time-of-flight positron emission tomography

Time-of-flight (TOF) positron emission tomography (PET) can improve signal-to-noise ratio (SNR) relative to conventional PET by improving coincidence localization and reducing random coincidences. Several time-of-flight positron emission tomographs were developed in the 1980s and early 1990s. However, interest in time-of-flight waned because of the low stopping power and light yield of the scintillators available at that time. Now newly discovered scintillators with greater light yield and/or stopping power, along with advances in photomultiplier tubes and electronics, are rekindling interest in TOF. To facilitate investigations into the utility of TOF, we have modified the SimSET simulation to track and bin TOF differences between coincidence photons. Images were reconstructed from simulated data using confidence-weighted backprojection and filtered backprojection. These images were used to investigate the effect of TOF on SNR. SNR improves dramatically with improved TOF resolution. However, the improvement is somewhat less than that predicted by a widely used theoretical model