Time-of-flight precision and PET image accuracy

Time of flight information is used in PET to improve image quality. However, the nature of the improvement and its relationship with the precision of the time of flight measurement remains to be well-characterized, particularly in the framework of iterative reconstruction. In this work, hot-spheres phantoms are imaged, and the list data are then degraded to simulate systems with poorer timing resolution. More precise of flight is found to lead to images with higher sphere contrast and lower background noise at each iteration, and convergent sphere contrast with fewer iterations. Combining these effects, the background noise at which each sphere reaches 90% of its final contrast is lower with improved timing resolution, with the amount of noise reduction underestimated by a conventional proportionality to the timing resolution.