Improving time resolution in time-of-flight PET

The last ten years have seen the development of the present generation of commercial time-of-flight (TOF) positron emission tomography (PET) scanners, based on LSO and LYSO scintillators and characterized by a time resolution in the 500–600 ps range. This is far from the intrinsic timing limits of such scintillators, which is in the order of 150–200 ps. Great benefits can be obtained from improved time resolution, given the direct effect of such a resolution on the image quality of TOF PET. The different contributions to the system time resolution of a TOF PET scanner are discussed, and some possible avenues for achieving better timing are presented.