Lawrence Berkeley National Laboratory

PET scanners based on LSO have the potential for significantly better coincidence timing resolution than the 6 ns fwhm typically achieved with BGO. This study analyzes the performance enhancements made possible by improved timing as a function of the coincidence time resolution. If 500 ps fwhm coincidence timing resolution can be achieved in a complete PET camera, the following four benefits can be realized for whole-body FDG imaging: 1) The random event rate can be reduced by using a narrower coincidence timing window, increasing the peak NECR by ~;50 percent. 2) Using time-of-flight in the reconstruction algorithm will reduce the noise variance by a factor of 5. 3) Emission and transmission data can be acquired simultaneously, reducing the total scan time. 4) Axial blurring can be reduced by using time-of-flight to determine the correct axial plane that each event originated from. While time-of-flight was extensively studied in the 1980's, practical factors limited its effectiveness at that time and little attention has been paid to timing in PET since then. As these potential improvements are substantial and the advent of LSO PET cameras gives us the means to obtain them without other sacrifices, efforts to improve PET timing should resume after their long dormancy.