A Monte Carlo positronium decay source model with multiple annihilation channels in GATE
Abstract
Positronium-based imaging requires realistic modelling of positronium (Ps) decay in matter. We introduce a modular Ps decay model implemented in GATE 9.4 and GATE 10, enabling the definition of an arbitrary number of decay channels characterised by lifetime, branching fraction, annihilation multiplicity (2g/3g), and optional prompt photon emission. The model is validated through analytical and numerical benchmarks, including lifetime distributions, branching fraction consistency, photon kinematics, and prompt photon emission. Its practical applicability is demonstrated using simulations of mixed annihilation scenarios and the NEMA IEC phantom with a large field-of-view PET system. The proposed model accurately reproduces input lifetime distributions as weighted sums of exponential components and correctly samples decay channel fractions. Simulated two- and three-photon annihilation kinematics are consistent with theoretical expectations. Complex mixtures of decay channels, including varying 3g-to-2g ratios and multi-component ortho-positronium lifetimes, are correctly modelled, with observable signatures reflected in both temporal and energy distributions. Phantom simulations demonstrate the capability to generate realistic positronium-sensitive datasets. This work provides the first general-purpose, multi-channel positronium decay model integrated into GATE, enabling realistic simulations of positronium behaviour in complex media. The model supports the development and optimisation of positronium-based imaging techniques, including PLI and multi-photon PET, and applies to medical imaging, industrial tomography, and fundamental physics studies. Its public availability and compatibility with standard GATE workflows make it a valuable tool for the broader research community.
Versions
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BibTeX
@misc{krzemien2026monte,
title = {{A Monte Carlo positronium decay source model with multiple annihilation channels in GATE}},
author = {Wojciech Krzemien and Mateusz Bala and Kamil Dulski and Wojciech Zdeb and Aurélien Coussat and Beatrix C. Hiesmayr and Konrad Klimaszewski and Michał Obara and Lech Raczyński and Roman Y. Shopa},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2605.14987},
eprint = {2605.14987},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.14987},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A Monte Carlo positronium decay source model with multiple annihilation channels in GATE
AU - Wojciech Krzemien
AU - Mateusz Bala
AU - Kamil Dulski
AU - Wojciech Zdeb
AU - Aurélien Coussat
AU - Beatrix C. Hiesmayr
AU - Konrad Klimaszewski
AU - Michał Obara
AU - Lech Raczyński
AU - Roman Y. Shopa
PY - 2026
DA - 2026/08/09
PB - arXiv
DO - 10.48550/arxiv.2605.14987
UR - https://arxiv.org/abs/2605.14987
AB - Positronium-based imaging requires realistic modelling of positronium (Ps) decay in matter. We introduce a modular Ps decay model implemented in GATE 9.4 and GATE 10, enabling the definition of an arbitrary number of decay channels characterised by lifetime, branching fraction, annihilation multiplicity (2g/3g), and optional prompt photon emission. The model is validated through analytical and numerical benchmarks, including lifetime distributions, branching fraction consistency, photon kinematics, and prompt photon emission. Its practical applicability is demonstrated using simulations of mixed annihilation scenarios and the NEMA IEC phantom with a large field-of-view PET system. The proposed model accurately reproduces input lifetime distributions as weighted sums of exponential components and correctly samples decay channel fractions. Simulated two- and three-photon annihilation kinematics are consistent with theoretical expectations. Complex mixtures of decay channels, including varying 3g-to-2g ratios and multi-component ortho-positronium lifetimes, are correctly modelled, with observable signatures reflected in both temporal and energy distributions. Phantom simulations demonstrate the capability to generate realistic positronium-sensitive datasets. This work provides the first general-purpose, multi-channel positronium decay model integrated into GATE, enabling realistic simulations of positronium behaviour in complex media. The model supports the development and optimisation of positronium-based imaging techniques, including PLI and multi-photon PET, and applies to medical imaging, industrial tomography, and fundamental physics studies. Its public availability and compatibility with standard GATE workflows make it a valuable tool for the broader research community.
ER -