Measuring the Three-Photon ortho-Positronium Decay in Positron Emission Tomography

Conventional Positron Emission Tomography (PET) systems do not utilize events resulting from ortho-Positronium (o-Ps) annihilation for image reconstruction. However, the information from the annihilation of o-Ps in 3 photons can significantly contribute to the obtained image quality, since the immediate determination of the annihilation point (vertex) becomes possible. In order to study the advantages of a PET modality with 3 photon positronium decay, the construction of a prototype detection system, consisting of one fixed and two movable detectors, is proposed (3γ-PET system). Having investigated the angular distribution of the three photons through kinematic simulations, the detectors will be placed in appropriate positions to detect the desired events. The main purpose of this work is the kinematic study of o-Ps decay in 3γ, in order to explore the angular and energy distribution of photons as well as the expected contribution of the background radiation. Development of an electronic system for the measurement of triple coincidence based on Pulse Shape Analysis (PSA) technique will be discussed.