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Optimization of positronium imaging performance of a simulated modular J-PET scanner using GATE software

Parzych Szymon

Bio-Algorithms and Med-Systems

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2023

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Vol. 19, no. 1

80--86

EN

Recently, a novel PET imaging method - positronium imaging - has been proposed to take advantage of previously unused information about the positronium states. The first ex-vivo and in-vivo images of positronium characteristics were acquired with the J-PET tomograph. Complementary to the standard annihilation photon’s detection, positronium imaging also requires the registration of the prompt photon, which follows β+ decay. To that end, the introduction of an additional energy threshold for prompt γ registration and optimization of the energy window for annihilation γ are required. This simulation-based work undertook the mentioned task in the case of the modular J-PET scanner. Based on the 44Sc radioisotope, the energy window for annihilation photons was established to 0.2 MeV - 0.37 MeV, while the threshold for prompt gamma was fixed at 0.37 MeV, closely following the end of the energy window for annihilation photons.

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Exploration of simultaneous dual-isotope imaging with multiphoton modular J-PET scanner

Beyene Ermias Y., Das Manish, Durak-Kozica Martyna, Korcyl Grzegorz, Mryka Wiktor, Niedźwiecki Szymon, Parzych Szymon, Tayefi Keyvan, Walczak Rafał, Wawrowicz Kamil, Stępien Ewa, Moskal Pawel

Bio-Algorithms and Med-Systems

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2023

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Vol. 19, no. 1

101--108

EN

The modular J-PET scanner, comprising 24 compact and versatile modules, each consisting of 13 plastic strips with four SiPM detectors at the ends, represents a powerful tool for clinical applications in nuclear medical imaging. This study presents preliminary results from the exploration of simultaneous dual-isotope imaging using the modular J-PET system. Our approach involved two isotopes: 68Ge, characterized by a ringlike shape, and 22Na, exhibiting a point-like shape. The imaging was based on double-coincidence and triple-coincidence events. In the double coincidence case, both isotopes contributed comparably, whereas in the triple coincidence case 22Na dominated due to the prompt gamma being emitted with 100% of positron emissions, unlike 68Ga, where the prompt gamma was emitted in only 1.3% of cases after positron emission. In this work we present direct 2γ images determined for two-signal events and images for three-signal events, with two signals from annihilation photons and one from a prompt gamma. These results showcase the preliminary findings from simultaneous dual-isotope imaging of 68Ga and 22Na isotopes using the modular J-PET scanner, which will be presented and discussed.

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Estimating the efficiency and purity for detecting annihilation and prompt photons for positronium imaging with J-PET using toy Monte Carlo simulation

Das Manish, Mryka Wiktor, Beyene Ermias Y., Parzych Szymon, Sharma Sushil, Stępień Ewa, Moskal Paweł

Bio-Algorithms and Med-Systems

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2023

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Vol. 19, no. 1

87--95

EN

The positronium imaging technique represents a potential enhancement of the PET imaging method. Its core principle involves employing a β+ radiation source that emits additional gamma (γ) quanta referred to as prompt gamma. Our aim is to evaluate the capability to differentiate between annihilation and prompt gamma emissions, a vital aspect of positronium imaging. For this purpose, the selected isotopes should enable high efficiency and purity in detecting both prompt gamma and annihilation gamma. The assessment of the efficiency in identifying prompt and annihilation photons for various isotopes, which are potentially superior candidates for β++ γ emitters, is conducted through toy Monte-Carlo simulation utilizing the cross-section formula for photon-electron scattering. In this article, we have performed calculations for efficiency and purity values across different isotopes under ideal conditions and examined how these values evolve as we incorporate the fractional energy resolution into the analysis. Ultimately, the primary goal is to determine the energy threshold that optimizes both efficiency and purity, striking a balance between accurately identifying and recording events of interest while minimizing contamination from undesired events.