3D PET list-mode iterative reconstruction using time-of-flight information

A limited number of time-of-flight (TOF) PET systems were developed and studied in the 1980*s and early 1990´s using fast scintillators such as BaF2 or CsF. These systems had the very good timing resolution needed for TOF PET but the lower stopping power and low light output yield of these scintillators could not provide systems with comparable performance to BOO. Recent development of other fast scintillators including LSO and LaBr3 has recently renewed interest in TOF PET. All of the TOF PET developed in the 80´s and 90´s used axial collimation with a very small axial FOV. Most TOF reconstruction methods that were studied were 2D. In this study, a 3D EM-ML list-mode iterative algorithm using TOF information has been implemented and tested using a new Monte Carlo simulation package, GATE, providing time information related to each photon travel from its annihilation to detection point and list-mode format output. Visually, it appears as if TOF information can improve detectability in reconstructed images.