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1 2025

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Optimising the event selection of the total-body J-PET scanner with a brain PET insert: A simulation study

Rädler Martin, Moskal Paweł

Bio-Algorithms and Med-Systems

2025

Vol. 21, Special issue: New Trends in Nuclear and Medical Physics

1--12

Objective: Positron emission tomography (PET) scanners with plastic scintillators offer more cost-effective instrumentation to image the distribution of radiopharmaceuticals. However, inter-detector scatters among plastic scintillators can lead to more false coincidences than in conventional PET scanners, since annihilation photons in plastic scintillators dominantly interact via Compton scattering, which deposits only a portion of the photon energy. A scatter test (ST), combined with a lower energy deposition threshold of 200 keV, has been used to preselect the coincidence events. Methods: In this work, we investigate the impact of temporal and spatial resolution limitations as well as a variation of the energy threshold on the preselection and different subsequent coincidence event selection policies via Monte Carlo simulations. We simulate the total-body Jagiellonian-PET (TB-J-PET), combined with a brain PET insert imaging a human-sized water phantom. Results: We find that coincidence time resolution (CTR) worse than 200 ps poses limitations on the ST for scanners close to the patient, such as the brain PET. Also, coincidence event selection requiring energy loss higher than 200 keV performs suboptimally, whereas a lower energy threshold (50 keV), combined with a time-based selection policy, can capture a higher percentage of true events, even under realistic time resolution. Conclusions: We recommend the adaptation of a time-based event selection policy together with a lowered energy threshold, which can also significantly increase sensitivity, as the latter rises faster than the fraction of true and non-phantom- -scattered events decreases. Dedicated analyses in the scatter-corrected image domain are necessary to further investigate this potential.