Feasibility study of the positronium imaging with the J-PET tomograph

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Abstract
A detection system of the conventional PET tomograph is set-up to record data from [Formula: see text] annihilation into two photons with energy of 511 keV, and it gives information on the density distribution of a radiopharmaceutical in the body of the object. In this paper we explore the possibility of performing the three gamma photons imaging based on ortho-positronium annihilation, as well as the possibility of positronium mean lifetime imaging with the J-PET tomograph constructed from plastic scintillators. For this purposes simulations of the ortho-positronium formation and its annihilation into three photons were performed taking into account distributions of photons' momenta as predicted by the theory of quantum electrodynamics and the response of the J-PET tomograph. In order to test the proposed ortho-positronium lifetime image reconstruction method, we concentrate on the decay of the ortho-positronium into three photons and applications of radiopharmaceuticals labeled with isotopes emitting a prompt gamma. The proposed method of imaging is based on the determination of hit-times and hit-positions of registered photons which enables the reconstruction of the time and position of the annihilation point as well as the lifetime of the ortho-positronium on an event-by-event basis. We have simulated the production of the positronium in point-like sources and in a cylindrical phantom composed of a set of different materials in which the ortho-positronium lifetime varied from 2.0 ns to 3.0 ns, as expected for ortho-positronium created in the human body. The presented reconstruction method for total-body J-PET like detector allows to achieve a mean lifetime resolution of ∼40 ps. Recent positron annihilation lifetime spectroscopy measurements of cancerous and healthy uterine tissues show that this sensitivity may allow to study the morphological changes in cell structures.
Funding Information
  • Austrian Science Fund (FWF-P26783)
  • Ministry for Science and Higher Education (6673/IA/SP/2016, 7150/E-338/M/2017, 7150/E-338/M/2018, 7150/E-338/SPUB/2017/1)
  • Fundacja na rzecz Nauki Polskiej (MPD, TEAM/2017-4/39)
  • Narodowe Centrum Nauki (2016/21/B/ST2/01222, 2017/25/N/NZ1/00861)
  • The Polish National Center for Research and Development (INNOTECH-K1/IN1/64/159174/NCBR/12)

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